Draft: Feature/aerosol with netcdf

Add a netcdf-cxx package for the netCDF-C++ interface.

This is work in progress, not to be merged right now.

The current implementation works, but:

1. Some propagated inputs are listed again, but only because the original netcdf package only list them as inputs even if they are actually needed at runtime. This should be fixed directly in the netcdf package.
2. As a first step, the package is written using netcdf-parallel-openmpi as input. It could be wise to either just use the sequential version and let the AeroSol package replace it with the parallel one, either write a variant netcdf-cxx as netcdf-cxx-parallel-openmpi.
3. The boost dependency needs to be added to AeroSol in order to correctly compile with netCDF.