Add NATLx8 grid

[adamrher]

What is the feature/what would you like to discuss?

CAM issue for adding the NATLx8 grid (SE-VR grid w/ 1/8deg refinement over North Atlantic)

ccs_config PR merged: https://github.com/ESMCI/ccs_config_cesm/pull/243 cmeps PR opened https://github.com/ESCOMP/CMEPS/pull/570 CLM PR not opened

Is there anyone in particular you want to be part of this conversation?

@rcjwills @islasimpson

Will this change (regression test) answers?

No

Will you be implementing this enhancement yourself?

Yes