added 'Eta' unit, not supported by udunits2
added a function to parse time deltas from formatted string in GAMAP created COARDS netCDF files
added Iris load callbacks (fixes) for netCDF files created with GAMAP
remove cube attributes imported from GAMAP's COARDS netCDF files (temp)
changed the names of cubes imported from bpch files to be consistent with those defined in GAMAP's netCDF files