Support for clavrx netcdf files

[joleenf]

Feature Request

The clavrx team is now producing netcdf files in real-time, for example see files in the AHI directory: ftp://ftp@ftp.ssec.wisc.edu/pub/clavrx/real_time/level2/ahi/

Currently, the clavrx reader only supports hdf files.

Solution
If possible, update the current reader to support both the old hdf and new netcdf files. If that is not the best solution, create a reader to support the new netcdf files.