More includes cleanup and code cleanup in the plugins (getting rid of the "stationindex" thing that was pretty much deprecated in all plugins)

The STD_PRESS spatial interpolation algorithm has been extended and can now deal with multiple input stations (with 2 different methods for handling this case). The Imis plugin now reads the air pressure and convert it to station air pressure (instead of sea level). Otherwise, improved error messages in libsmet and documentation / minor code cleanup.

An unpleasant bug has been fixed in data_converter when handling large number of stations and time ranges. Minor code cleanup in some plugins.

In order to add 3D grid reading/writing methods to the plugins, the whole architecture of IOInterface has been changed: this is not a purely virtual class anymore, it now always implements the "nothing implemented here" exception. This makes the plugins more compact (there is no need to implement empty methods for what the plugin can not support) and much clearer. The documentation and template have been changed acoordingly.

Several exceptions have been renamed in order to be more generic (ex: instead of FileNotFound -> NotFound) and their text has been modified accordingly. The GSN plugin now reports the errors with more relevant details (invalid sensor name, no permissions).

Fixed a small bug in the MERGE feature and small improvements to the GSN plugin (always set a station ID, up to date documentation, more possibilities in the parameters names matching). Otherwise, minor code cleanup.

Small documentation update and relying on views for two more queries to the database (only one query remains that does not rely on views).

Micro optimizations for Sun.cc, converted an exception into a warning in ImisIO and fixing case in message in Smetio

Code cleanup and fix for IMIS: now the ENET stations receive the number 1 for the automatic stations instead of 0.

Finally, a long awaited (and MAJOR) change: HNW is gone, it is now PSUM. This name should be clearer and every occurences of "HNW" (even in temporary variables or algorithms) have been replaced by psum. A check is performed on keys containing "hnw" and an exception is thrown if some are found, urging the user to update the ini file. Please keep in mind that the calling codes have to now refer to MeteoData::PSUM and that some algorithms are now named differently!

The K_TO_C and C_TO_K macros have been replaced by static methods in the IOUtils namespace. They now properly check for nodata in order to avoid weird values and outputs...

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When using Snowpack simulations in the database for computing precipitation, this was leading to lots of very small events. This should now produce less events but with more precipitation.

better file structure: all the classes purely focused on data storage (such as grids, dates, etc) have been moved into a "dataClasses" directory. All subdirectories are nhow named similarly to the classes and methods: the words after the first one are capitalized.

The cmake files for compiling with LibXML++ have been updated since they would not work with more recent Linux (but we should consider dropping LibXML++ and only rely on LibXML2 in order to reduce the dependencies and package finding mess). The special points are now called POI (Points of Interest, like for a gps device) in order to make them more familiar.

fixing issue 303: if swe>0, then we accept all delta_swe>=0 (since 0 is also a valid value!). Moreover, it is now possible to properly generate a composite HNW: IMIS in the summer and Snowpack in the winter.

Fixing some warnings for Visual C++ and also using ostringstream instead of stringstream when appropriate

More size_t fixes (ie trying to be consistent) and a bug was found when spatially interpolating using a few specific algorithms that would not reset their internal vectors between two calls (thanks Matteo for helping uncover this bug!)

More changes, according to "Using OCCI: best practices - An Oracle White Paper - May 2003". Now the same Statement object is used accross multiple querries (to reduce memory reallocations).

Data prefetching is now turned ON in Oracle querries, leading to a x2 speed up (global speed up measured on data_converter)

The Config class now has a method getValues() to retrieve in a vector of type T all values whose keys match a given pattern. This makes it possible to retrieve in one call all the Input::STATIONx values even in the case of discontinuous numbering (issue 341) as well as easily get the number of stations declared in io.ini (issue 220). This number of stations is not guaranteed to work (since some plugins don't list the input stations in io.ini) but should guide memory allocation in user code anyway.

A reference has been fixed in Suntrajectory, redundant errort checking has been removed from GeneratorAlgorithms.

Trying to help the compiler use SIMD instructions for some array operations. Small documentation improvement for IMISIO.

My previous commit was terrible... it simply made it impossible to define optional keys. This has now been fixed but required a change in the API. So, don't use Config::nothrow but IOUtils::nothrow instead.

In order to try to be closer to the spirit of the STL, now the empty strings/vectors/lists are tested with .empty(), the first/last elements of vectors accessed with front()/back(), the empty strings are not contructed with string("") but with string(), etc This makes a benchmark based on meteo_reading ~4% faster and this makes the code suprisingly easier to read. 

Some extra constification took place as well as some minor code cleanup (optimizing the comparison between two vectors in order to perform less tests, etc).

The Date class can now properly generate and parse full ISO timestamps, including time zone information. The full specification is now supported by convertString() with a helper method in the Date class. Ouputing an ISO string with its time zone is done by requesting the ISO_TZ format.

The plugins used to keep a reference to a config object as provided by IOManager. But this was triggering some warnings (reference to an object that might disappear outside of the constructor), therefore it has been replaced by a const copy (it is not yet 100% sure if this is really better, but at least the compilers won't complain).

When a user was provinding IMISIO with a non-existing station name, the error messages were quite cryptic. In order to properly tell the user what happened, the code has been slightly reorganized. Some code clean up also took place in IMISIO.

Added an extra error message in ImisIO and a new method for Config: keyExists() to check if a given key is present (instead of always reading a key with nothrow, etc)

Some warnings have been fixed in the tests and all 'string tmp=""' or 'tmp=""' have been replaced by either an empty constructor (that does the same ) or tmp.clear() (that does the same too)

The cubic B-spline image resampling algorithm has been implemented in ResamplingAlgorithms2D. Various Weffc++ warnings have been fixed in PNGIO, ImisIO and GRIBIO, leading to the suppression of unused variables.

The plugins are no longer separately loadable libraries, but are fully incorporated into libmeteoio. All classes and facilities that provided capabilites for the dynamic loading were deleted (DynamicLibrary). IOPlugin now holds a function pointer to an instantiation function for children of IOInterface. In IOHandler::registerPlugins() all plugins need to be registered with the key name, the class name, a pointer to an instance of the class and a function pointer to the instantiation function for the class (child of IOInterface). IOInterface lost some complexity and thus the constructor of the base class does not have to be called in derived classes anymore.

The CMakeLists.txt files had to be updated to no longer make separate dynamically loadable libraries for each plugin, but to simply add the classes the user selectes to the meteoio library. 

As a side effect the io.ini key GENERAL::PLUGINPATH is no longer necessary.

Some extra documentation has been added for the UPS coordinate system. The coordinates test has been expanded. A missing default value has been added to the Suntrajectory.

Fixed some spelling mistakes in the tests, improved USE_IMIS_HNW comment in ImisIO, improved the serailize method in Meteo2DInterpolator (but it is not working yet and anyway of little interest), fixed a casting warning in MathOptim. Some warnings are now turned off for POPC.

Better error messages in IMISIO, better safety (regarding "undef") in Date and some code cleanup/const/reserve business (all benchmarked) for the others. We also now avoid stacking two "/" at the end of the PLUGINPATH if one is already present.

Investigating issue 210, it has been found that the IMIS precipitation had a division by 2 that was not required (halving the precipitation compared to what it should have been). This has been fixed.

Small documentation improvement in ResamplingAlgorithms.