Enhance support for rotated latlon grids and update related documentation.

[JohnHalleyGotway]

Describe the Task

MET #1029 added partial support to MET for rotated lat/lon projections.

A comment from #1029:
Randy finished this for the met-8.0 for GRIB2, MET NetCDF, and the python interface.
May still need to be added for GRIB1 and CF-Compliant NetCDF.

This task is to...

• Add support for rotated lat/lon grids as grid specification strings.
• Review/update the documentation, as needed.

I am not able to add support for rotated lat/lon grids for the GRIB1 or NetCDF CF-compliance libraries since I cannot find any sample input data files. Rotated lat/lon is listed as a possible grid type in GRIB1 documentation (https://www.nco.ncep.noaa.gov/pmb/docs/on388/table6.html), but I am unable to run copygb to generate a sample data on that project.

This issues arose via met-help:
https://rt.rap.ucar.edu/rt/Ticket/Display.html?id=97502

Time Estimate

4 hours

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[JohnHalleyGotway]

• Re-tested GRIB2 and MET NetCDF for rotated lat/lon and confirmed that it works.
• Re-tested python embedding for rotated lat/lon and confirmed that it works.
• Consolidated and simplified the documentation of the grid specification string and python embedding dictionaries.
• Updated grid specification string parsing logic to handled rotated lat/lon grid spec strings.