Add ability of mksurfdata_esmf to create datasets that can be used for Paleo work...

We want to have some customized files in place, in order to allow mksurfdata_esmf to create surface datasets that can be used for Paleo work for CLM6.0. The Paleo working group will support these specific datasets. A specific development project for this is the Last Glacial Maximum (LGM). There was work on this in CLM4.0 for CESM1.2.2, but we need to extend this to the latest ctsm and for CLM6.0. So there are some modern raw datasets that were added in that would need to changed to correspond to paleo conditions.

This won't be an out of the box feature. So there won't be a simple option to do this. But, the user can modify the namelist that gen_mksurfdata_namelist creates and put in the specific Paleo datasets that are supported by the Paleo group, and then create a surface dataset that way, customizing a batch script to submit it on Derecho.