+Specify CVMix parameter units and rescale CVMix

  Specify the units of 5 parameters and applied dimensional rescaling to 14
MIN_THICKNESS or other length or viscosity parameters used in the CVMix code to
appropriate units like [Z ~> m] or [Z2 T-1 ~> m2 s-1], with related changes to
the rescaled units of several other internal variables.  Also added comments
describing a number of internal variables and their units in the MOM_CVMix and
MOM_tidal_mixing code.  The preliminary internal calculations in these routines
now work in these [Z ~> m] units a bit longer before being recast into MKS units
for the calls to the CVMix routines.  The unused KPP runtime parameters
CORRECT_SURFACE_LAYER_AVERAGE and FIRST_GUESS_SURFACE_LAYER_DEPTH have been
marked as obsolete in comments of the code since 2015, and have now been
formally obsoleted.  All answers are bitwise identical, but there are changes to
some MOM_parameter_doc files.

src/diagnostics/MOM_obsolete_params.F90

@@ -83,7 +83,8 @@ subroutine find_obsolete_params(param_file)
 
   call obsolete_real(param_file, "ETA_TOLERANCE_AUX", only_warn=.true.)
   call obsolete_real(param_file, "BT_MASS_SOURCE_LIMIT", 0.0)
-
+  call obsolete_real(param_file, "FIRST_GUESS_SURFACE_LAYER_DEPTH")
+  call obsolete_logical(param_file, "CORRECT_SURFACE_LAYER_AVERAGE")
   call obsolete_int(param_file, "SEAMOUNT_LENGTH_SCALE", hint="Use SEAMOUNT_X_LENGTH_SCALE instead.")
 
   call obsolete_logical(param_file, "MSTAR_FIXED", hint="Instead use MSTAR_MODE.")