generalize the combinations available for cpld_gridgen

[DeniseWorthen]

The cpld_gridgen utility currently works only for specified combinations of the ocean and atm. It should be generalized to create any ATM and OCN resolution. This will provide the required mapped ocean mask for any ATM resolution with any OCN resolution.

Originally these combinations were "pinned" to certain combinations because of the need to generate a set of weights for the CICE IC generation. Since this capability has been replaced by the ocnice_prep utility, all mapped ocean combinations can now be generated at once in cpld_gridgen.