Python converter for Msonet prepBUFR (#181)

- This PR adds a Python converter for the Msonet prepbufr data. 

- This converter will be used to convert Msonet prepbufr data to IODA
(netCDF) format. Following steps similar to GDASApp, a Python file and a
Json, description file were created. In its current form, this converter
can be run using the ~ush/ioda/bufr2ioda/run_bufr2ioda.py script of the
GDASApp.

- The following two files are new: 
1. ~/IODA/python/bufr2ioda_msonet_prepbufr.py
2.  ~/IODA/python/bufr2ioda_msonet_prepbufr.json

- Related issue #123

---------

Co-authored-by: Praveen Singh <pkumar@hercules-login-3.hpc.msstate.edu>
Co-authored-by: Guoqing Ge <guoqing.ge@noaa.gov>
Co-authored-by: Praveen Singh <pkumar@hercules-login-2.hpc.msstate.edu>
Co-authored-by: Praveen Singh <pkumar@hercules-login-1.hpc.msstate.edu>
Co-authored-by: Samuel Degelia <samuel.degelia@noaa.gov>

rrfs-test/IODA/python/bufr2ioda_msonet_prepbufr.json

@@ -0,0 +1,11 @@
+{
+  "data_format"     : "prepbufr",
+  "data_type"       : "MSONET",
+  "cycle_type"      : "rap",
+  "cycle_datetime"  : "{{ current_cycle | to_YMDH }}",
+  "dump_directory"  : "{{ DMPDIR }}",
+  "ioda_directory"  : "{{ COM_OBS }}",
+  "subsets"         : [ "MSONET" ],
+  "data_provider"   : "U.S. NOAA",
+  "data_description": "MESONET SURFACE REPORTS (COOPERATIVE NETWORKS)"
+}