Support creation from GRIB metadata

[dcherian]

GRIB files come with coordinate system specified through attributes like this:

 'GRIB_DxInMetres': 3000.0,
 'GRIB_DyInMetres': 3000.0,
 'GRIB_LaDInDegrees': 38.5,
 'GRIB_Latin1InDegrees': 38.5,
 'GRIB_Latin2InDegrees': 38.5,
 'GRIB_LoVInDegrees': 262.5,
 'GRIB_NV': 0,
 'GRIB_Nx': 1799,
 'GRIB_Ny': 1059,
 'GRIB_gridDefinitionDescription': 'Lambert Conformal can be secant or tangent, conical or bipolar',
 'GRIB_gridType': 'lambert',
 'GRIB_iScansNegatively': 0,
 'GRIB_jPointsAreConsecutive': 0,
 'GRIB_jScansPositively': 1,
 'GRIB_latitudeOfFirstGridPointInDegrees': 21.138123,
 'GRIB_latitudeOfSouthernPoleInDegrees': 0.0,
 'GRIB_longitudeOfFirstGridPointInDegrees': 237.280472,
 'GRIB_longitudeOfSouthernPoleInDegrees': 0.0,

This code in pygrib converts to a proj4 string.

Would it be in scope to create a CRSIndex from such metadata. It appears that first translating to a proj4 string would be easiest.

cc @blaylockbk