Implement support for log levels in MPAS dynamical core

* The following log levels are supported:
  * log_level_quiet (a.k.a. debugout_none in CAM-SIMA)
  * log_level_info (a.k.a. debugout_info in CAM-SIMA)
  * log_level_verbose (a.k.a. debugout_verbose in CAM-SIMA)
  * log_level_debug (a.k.a. debugout_debug in CAM-SIMA)
* Log messages that originate from CAM-SIMA side are prefixed by
  "MPAS Interface (N): ", where N is the MPI rank
* Log messages that originate from MPAS side are prefixed by
  "MPAS Subdriver (N): ", where N is the MPI rank
* Log messages have been improved to be more descriptive and user-friendly