MPAS-A dycore workflow and additional compset support

This issue will identify how best to support the MPAS workflow within the CESM framework. The workflow includes procedures, data, code, and supporting scripts and applications which are required to create the initial and boundary data needed to run CAM-MPAS. Some MPAS workflow functionality may be easily ported to parallel functionality within the CESM framework while other aspects will be unique and will add to CIME and or/the existing suite of CESM offline tools.

Proposed MPAS functionality to be ported into existing framework
- Provide automatic decomposition for MPAS given a user-specified number of PES. Will require duplicating MPAS-A application (metis) functioality or building and calling metis from CIME/build-namelist

Additional CESM framework functionality needs:
- Complete datasets for a default set of resolutions proposing .25,.5,1, and 2 degrees - CESM required metadata
- Dycore tuning defaults for different resolutions
- Physics tuning defaults for different resolutions (CLUBB, etc.)
- Simple model/SCAM dataset support for CAM4/5/6 (requires 26/30/32 model levels in initial files)
- WACCM support
- CESM doc update and pointers to MPAS documentation. Just looking at the namelist documentation and noticing that descriptions of namelist options are very sparse and not very useful for users. (For instance where there is a list of valid settings only the default is described).