Add the optional conversion argument to register_diag_scalar, which works
analogously to the argument that is already available in register_diag_field.
All answers are bitwise identical, but there is a new optional argument in a
public type.

  Use conversion argument during registration and tmp_scale argument in the
calls to global_area_mean for averaged fields in the MOM_forcing_type and
MOM_diagnostics modules.  Also added or corrected some descriptive comments and
fixed an extra unit conversion factor in one recently added calculation of ustar
that was likely not used.  All answers are bitwise identical.

  Use the tmp_scale argument in calls to global_area_integral to simplify some
global integrals, and added dimensional rescaling for the time_step element of
the ice_shelf control structure.  Also corrected some dimensional descriptions
in comments.  All answers are bitwise identical.

  Rescaled the new_depth variable in apply_topography_edits_from_file, and used
source arguments to initialize 6 allocated variables.  All answers are bitwise
identical.

  Replaced a call to global_area_mean with a call to global_area_integral in a
diagnostic calculation in the internal_tides module.  Also added descriptions of
the dimensions of a number of variables in this module, or eliminated the
dimension description of several integers (for which units make no sense).  Only
an unused debugging diagnostic is changed, and all solutions are bitwise
identical.

  Eliminated units arguments for logical, integer, or character string get_param
calls where the units make no sense.  In some other cases, calls were slightly
revised to place the units and scale arguments on the same line for easier
detection of inconsistent settings.  All answers are bitwise identical, but
the MOM_parameter_doc.all files for some test cases are corrected.

  Revised get_param calls to put the units and scale arguments on the same line,
to help detect inconsistent settings.  All answers and output are bitwise
identical.

  Eliminated a commented-out get_param call and use a source argument to
initialize some arrays.  All answers and output are bitwise identical.

  Corrected the units in some get_param calls in the dumbbell test case.  All
answers are bitwise identical, but there will be minor changes in the
MOM_parameter_doc files for the dumbbell test case.