A few errors have also been fixed for Snowpack (missing the SNOW_WRITE
key and wrong type for HOAR_DENSITY_BURIED)

This is necesary for the packaging (it is much beter to have an
"inishell-apps" folder in /usr/share than an "applications" folder)

When both a default value and precision=... where provided in the xml
file, the precision was reset to the default precision. Now the default
precision is reset to the XML provided precision.

In order to give the user the required flexibility to enter the numeric
values he/she wants to, precision specifications have been almost
everywhere in the xml files (a few places still rely on the default
settings because it makes sense). The units have also been added where
possible.

The goal being to avoid writing out lots of keys that already have
defaults in their respective applications

It is not perfect in the sense that the 2DInterpolation section must be created anyway, independently of the use of spatial resampling or not. The same applies to the Grids2D configuration frame. A message is shown to the user, explaining when these should be used...

Now the meteoio_plugins and meteoio_gridplugins files are not needed anymore, they have been replaced by more modular files. The new syntax for the WINSTRAL spatial interpolation has been implemented. A buggy input field in Snowpack has been fixed (NUMBER_OF_SOLUTES).

The XML files had inconsistent case for the section names, this has been fixed. A mis-indenting has been fixed in help_dev.xml

Thanks to the includes, we are now much more granular. But more work is needed with better handling of defaults, more thoughts about colors and making sure all MeteoIO and Snowpack keys are represented.