Remove "fake MPI" capability in serial/ice_communicate.F90
  Add ssh_stress variable/namelist with options 'geostrophic' or 'slope' to specify the computation of the sea surface height stress term.
  Add ssh_stress to ice_in, set to 'geostrophic'.
  Add ssh_stress to namelist documentation
  Change "coupled" to CESMCOUPLED in ice_init on check for oceanmixed_ice setting
  Clean up drivers
    remove "coupled" and CESMCOUPLED from standalone/cice as if neither were set
    remove "coupled" macro end_run call in nuopc/cmeps, CESMCOUPLED left mostly alone
    remove "coupled" and CESMCOUPLED from mct/cesm1 as if both were set
    remove "coupled" and CESMCOUPLED from direct/hadgem as if both were set
    no changes to nuopc/dmi, prefer dmi make those changes
Fix error in coriolis namelist documentation where Cstar was in the wrong place

NOTE: Coupled systems should leverage the new ssh_stress namelist to turn on the 'slope' option.  The coupled CPP flag is no longer in use.