NetCDFIO: Further cleanup, readStationData revamped, added a method to check dimensions of a variable

NetCDFIO: Thanks to heavenly input by Mathias the 2D grid reading and writing is numerically consistent now. The only tradeoff is that precision of the cellsize is limited to 1cm, otherwise numerical instabilities may occur. 

NetCDFIO: deleting existing files before creating a new one when writing meteo data, everything else is too complicated for the moment

A new constructor has been implemented for the GridObjects as well as better members alignement. A potential issue with Winstral has been fixed. A wind direction algorithm has been implemented according to Ryan, 1977.

Several bugs have been fixed: in the AllSky generator, the cloudiness was still forced to 0.5 (as for debug). The data creators were also called *after* the generators, thus making it impossible to used a created data in a generator. 

The placeholders have been put in place (but commented out) for the cloudiness/tau_cloud/clearness index support in MeteoData. It seems that Kt=clearness index might be the proper way to go, but this is still a messy field. Some comments have been added in the code to clarify the use of such parameters.

NetCDFIO: reading of meteo data from FORCING.nc implemented, cleanup and correct conversion of units necessary.

Data Creators have been defined: it is now possible to create an extra parameter from a data generator. Simply define it as {param_name}::create = {generators} in the [Generators] section and the parameter will be created from any data generators specified (beside the "create" syntax, everything is currently identical with data generators).

The Idso clear sky ILWR has been added (and also added to the clear sky generator). Some (dead) code that was committed by mistake has been removed and the very begining of what will be needed for data creators put in place (still some way to go!).

The ClearSky and AllSky generators have been renamed as ClearSky_LW and AllSky_LW for clarity. The debug outputs (.toString()) have been improved. The Config::findKey method is now able to do pattern matching anywhere in the string (if "anywhere=true"). This makes some code simpler (for generators). 

The parameter copy feature has a new syntax: TA2::COPY = TA will copy TA into TA2 (clearer and more consistent). Please update your ini files if necessary!

Several improvements to Winstral: the mass balance conservation is now properly enforced and this exposed a few bugs that have been fixed. This is not yet ready to use, though: the wind direction is still hard coded!

The first algorithm implementing (Winstral, 2002) is now being tested. This seems to work but the mass balance still has to be validated. The IOManager can now be constructed directly with a io.ini file name. Some code clean up has been performed in InterpolationAlgorithms.

The possibility to force the input file encoding has been added (for broken XML files) and several bugs fixed when reading all files in a directory

In COSMOXMLIO, it is now possible to choose between using the station location or the model location with an argument in the ini file

Two extra clear sky parametrizations have been added, including one for desert conditions. They are available to the ClearSky generator. Small code and documentation cleanup.

Finally, the AllSky data generator is in good shape. It properly caches the previous valid cloudiness value for each station, a bug in the cloudiness calculation has been found (for low sun angles)and the documentation is now in order. We just need to get a cloudiness parameter in MeteoData in order to also be able to read measured cloudiness!

More improvements to the AllSky data generator: it now computes the cloudiness if none is provided. Another improvement will have to be brought for working with multiple stations as well as adding the cloud fraction to the MeteoData parameters! (ie: stay tuned!)

Fix for issue 366: DEMObject buffering, it was buffered in a map as Grid2DObject, now in a vector as DEMObject.