Netcdf Rasdaman: NA values, CF conformity, crs readable, 3d netcdf not possible

[przell]

Some issues to netcdf output from rasdaman:

• netcdf output should also work on datacubes of all dimensionality not only 4d
• netcdf output should be CF conform
• netcdf output should have the crs readable
• Handling of NAs??? In NDVI collection the designated NA value is a number in the ouptut. I think in VHI it is returned as NA. At least we need a documentation for this for the users. Otherwise area means could give really really wrong results (eg if -32768 should be NA but is used in the backend)