Unify CDEPS gfs, cfsr, and gefs datm datamodes + Improve error checking in rt.sh (2388) + Add ability to read increment files on native cubed sphere grid (2304)

Unify CDEPS gfs, cfsr, and gefs datm datamodes + Improve error checking in rt.sh (2388) + Add ability to read increment files on native cubed sphere grid (2304) #6046