Unresolved issues:

Surface elevation check
! Reject obs if the station height is far way from the model terrain.

but fwd operators (rttov) need these surface values
see discussion #332

Code:

branch (be aware I may force push to this)
https://github.com/NCAR/DART/tree/mpas-refactor

Spec (note 7 v 8)
https://docs.google.com/document/d/1wD4MKM5PquOUbxK3YxIjcbIaFThJfa318heDn_bFUbs/edit