Merge branch 'update/mpasa_grids_v7.3' into develop (#57)

Include changes to EWOrg/CAM:
- comment out cam_dev grids that produce unrealistic atmosphere that
  causes cases to fail
- revert MPAS-A to a v7.3 non-OpenACC version to address correctness
  issues

Externals.cfg

@@ -6,7 +6,7 @@ local_path = ccs_config
 required = True
 
 [cam]
-tag = cam-ew2.2.000
+tag = cam-ew2.2.002
 protocol = git
 repo_url = https://github.com/EarthWorksOrg/CAM
 local_path = components/cam