Replace netcdf-decoders in the data processing pipeline

[dopplershift]

The point data that the Unidata TDS serves is currently being decoded by the netcdf-decoders package:

http://www.unidata.ucar.edu/downloads/decoders/index.jsp

which uses the netcdf-perl library:

https://github.com/Unidata/netCDF-Perl/blob/master/README.md

The decoders and the netcdf-perl library have been deprecated and have some issues with them that need to be addressed.

Rather than addressing them in their current implementation, we should totally remove reliance on these decoders for data that we serve through the TDS.

Subtasks:

• Replace Upper Air Decoder Script (ua2nc) Use MetPy's upper air decoding functionality (Upper Air Parsing MetPy#71).
• Replace METAR decoder. Use MetPy METAR decoder (METAR parsing MetPy#70)
• Replace Buoy and Synoptic Decoders (buoy2nc, syn2nc). Actual decoding should be in MetPy.

Taken from TDS-643, TDS-685, TDS-686, TDS-687