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

The method "waterSaturationPressure" has been renamed as "vaporSaturationPressure" and a reference added.

The MOD operator has been added to Date (it takes a number of seconds in argument). This is used by the new VSTATIONS_REFRESH_RATE key to avoid calling the spatial interpolations too often in the virtual stations. More checks have been implemented in the virtual stations and dowscaling for added safety. 

A major bug has been found when reading 3D grids in ARPS: the indexes when not in the right order.

Fixed a bug when reading 3D fileds, improved the documentation and renamed a method to a more proper name

The layers handling is not so clear... it seems that the first layer is most often a purely numeric layer and therefore must be skiped. Some fields may not have such a layer, this will have to be clarified.

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.

A bug has been fixed: there was a confusion between the mean adiabatic lapse rate and the dry one. Small code cleanup in DEMObject (with a better toString() method), ARPSIO and ProcShade.

Lots of small improvements and bug fixes for reading ARPS files. Now the 2D grids should work quite well but the 3D grids are still some kind of a hack... 

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).

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 This name should be clearer and every occurences of "HNW" (even in temporary variables or algorithms) have been replaced by psum.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!

Trying to close some potential security flaws (using FlawFinder). All files opened for reading are now checked and special files (devices, etc) are refused.

The grids.isEmpty() method has been renamed as empty() in order to follow the STL convention. The ARC grids written with Alpine3D naming were still not properly named, they should now be directly recognized by the Alpine3D grid viewer.

The basic operators have been implemented in Grid2DObject and Grid3DObject as well as DEMObject (with the proper update strategy). 

In order to suppress the risk of out of date "ncols, nrows" and since these were redundant with Array2D<>.nx/ny, they have been suppressed and it is therefore now mandatory to rely on the getNx/getNy/getNz getters. This is much safer but impacted quite a lot of code... 

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 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!)

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.

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)

Last general warnings from Weffc++ addressed and we now move a step further: almost all the "deep" warnings as well as Weffc++ are now enabled in debug compilation.

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.

Fixing a small bug/warning in libsmet and properly initializing the members in some plugins (through initialization lists, as usual).

The MeteoData == operator now compares with an epsilon. The chekEpsilonEquality function has been rewritten, according to best practise and inlined. The powN functions have been moved to MathOptim and inlined. This makes the benchmarks 2% faster, that's such a victory...

Since the autotools are obsolete (and unmaintained) in MeteoIO, they have been removed. The popc++ version can be compiled with cmake (with some tricks: disable GSN and force the compiler to popcc). 

For consistency, the various definitions of ot_deg and to_rad have been suppressed and replaced by Cst::to_deg or Cst::to_rad. Some mentions of the Earth's radius have been replaced by Cst::earth_R0. In Coords, some variables have been declared as const.

A new getMeteo() method has been implemented that transparently performs spatial interpolations and returns a grid for a given parameter. This should be prefered to interpolate(), since it allows the reading plugin to directly provide gridded data (such as coming out of GRIB).
Code cleanup in ResamplingAlgorithms, improved error message in A3DIO. Several keys have been updated/added to the plugins, in order to be more consistent between plugins. Therefore, meteo file extensions are given with METEOEXT, grid2d extensions with GRID2DEXT, grid2d prefix with GRID2DPREFIX (not all plugins support them, though), etc

Some improvements for allowing the ARPS plugin to read u, v, w, etc from an ARPS file. Unfortunatelly, files edited with ARPSGRID are stripped of all markup for fields, so they are currently not supported. It also seems that not all files contain all possible fields, and even if they would, they would still miss some important field (like TA, RH, etc). This is therefore of little practical interest...

This addresses the 2D part of issue 168: the ability to specify which meteo parameter and time step to read/write from/to a 2D grid. This should be the prefered reading method in the future, since it leaves to the plugin the task of building the file name, extension, database table, etc This also provides added metadata and more control over the writing process.

SNIO throws an exception if the user specified a METAFILE that does not exists/is not valid. ARPSIO was wrongly reading grids (wrong layer for DEM and swapping x and y)