Example of conservative interpolation of SMB forçing for ISMIP6

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-* To try this example first get required data:
	- a mesh of the greenland Ice sheet in EPSG:3413 projection
		e.g.: http://elmerfem.org/elmerice/wiki/lib/exe/fetch.php?media=eis:greenland:present:greenland_mesh_v0.tar.gz
	- some reference SMB:
		e.g. results from MAR v3.9 averaged over 1980-1999
		ftp://ftp.climato.be/fettweis/MARv3.9/ISMIP6/GrIS/ERA_1958-2017/MARv3.9-ERA-Interim-1980-1999.nc

	- aSMB forcing from ISMIP6:
		e.g. ftp://searive@cryoftp1.gsfc.nasa.gov/ISMIP6/Projections/GrIS/Atmosphere_Forcing/aSMB_observed/v1/MIROC5-rcp85/aSMB
		if you don't have access to ISMIP6 data sets you can skip this an adapt the test.
        - a grid description file for the structured netcdf above
		e.g. ftp://searive@cryoftp1.gsfc.nasa.gov/ISMIP6/Grids/GrIS/GDFs/grid_ISMIP6_GrIS_01000m.nc

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-* Required external software and libraries:
	* CDO
	* netcdf
	* fortrangis with proj support


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RUN the example:
	1. get the data-sets (see above)
	2. adapt  Makefile.IN with the links to your install directories for fortrangis and netcdff
	3. Compile the solvers: make -f Makefile.IN
	4. RUN MakeCDOGridDesc.sif : 
		- this will produce an unstructured grid description file of the mesh for CDO
		- required fortrangis to compute (lon,lat) from (x,y) coordinates
		- restructured to 2D meshes with 303 elements only
	5. The script Interpolate.sh uses CDO for the conservative interpolation from the initial structured Grid to the Elmer unstructured grid. Results are given as cell values
	6. READ_CELL_NETCDF.sif shows how to read the unstructured netcdf to get the variable on the 2D mesh; eventually use conservative FE interpolation to convert the elemental variable to a nodal variable 
