+Refactor ALE_remap_velocities

  Refactored ALE_remap_velocities to separate the code setting the thicknesses
at velocity points from the code that actually does the remapping.  This
includes the creation of the new public routines ALE_remap_set_h_vel and
ALE_remap_set_h_vel_via_dz and the replacement the pair of tracer point
thickness arguments to ALE_remap_velocities and remap_dyn_split_RK2_aux_vars
with a pair of the old and new thicknesses at the velocity points and the
elimination of several arguments to these routines that are no longer being
used.  There are also new internal routines ALE_remap_set_h_vel_partial and
ALE_remap_set_h_vel_OBC to apply modifications to the velocity point thicknesses
with OBCs and one runtime option.  The runtime variable REMAP_UV_USING_OLD_ALG
has effectively been moved from MOM_ALE.F90 to MOM.F90, although it is still
being read in MOM_ALE_init for use with the accelerated regridding during
initialization.  All answers are bitwise identical, but there are two new
public interfaces and changes to the arguments to two other public interfaces
and a run-time parameter was moved between modules resulting in changes to
some MOM_parameter_doc files.