remove "multigrid" logical and associated code from the mesh cap

[DeniseWorthen]

Is your feature request related to a problem? Please describe.
The testing and use of the multigrid functionality w/in the mesh cap was never completely developed. It has not been tested in UWM for several years. No testing of any kind was done with multigrid=true in the mesh cap for the recently added netCDF+PIO capability. With the unstructured grid capability in the mesh cap, further development of multigrid in the mesh cap is unlikely. Un-tested and un-used features should be assumed to be broken, and should be removed.

Describe the solution you'd like
Remove the code blocks within multigrid=true logicals in the mesh cap.