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

very minor code cleanup, some comments were wrong and have been fixed, a wrong debug message has been fixed (in toString())

A gridBuffer class has finally been implemented (basically, moving the old grid buffering code into it) and is now in use for the GridsManager. An invalid file name in the examples has been fixed and a toString() debug message has been improved in the TimeSeriesManager.

The Buffer class is now used to buffer meteo time series. Since this is not (yet) a proper ringbuffer, all data is erased before pushing more data into a buffer (similarly to what it was before this commit). It has been tested with data_converter on numerous data (including with virtual stations) as well as with snowpack on operational stations.

Following a bug report from GeoTop, the add_to_cache() method that had been partially removed is now back, under a slightly different name: add_to_points_cache(). Otherwise, white spaces, copyright headings were modified and some pragmas added for VC++ in GSNIO and CosmoXMLIO.

In order to make it more modular and allow more advanced processing (virtual stations, downscaling, multiple io sources) the IOManager is now a proper wrapper: the processing is fully delegated to either a GridsManager or a TimeSeriesManager. These can in turn be reused at some other places (like in the Meteo2DInterpolator) to offer full buffering and processing of "local" time series. The buffering is now done by these two new classes (therefore the BufferedIOHandler class has been removed) and it is planned that dataClasses will be implemented for proper ringbuffers (one for time series, one for grids and one for isolated points) and receive the generic buffering code later on. 

A new fastPow(double, int) has been implemented for positive exponents. The begining of a generic handling of units also appeared in IOUtils. Finally, the ProcessingLevels are now defined in IOUtils instead of IOManager.