*+Corrected some oblique OBC restarts

  Added separate restart variables for some of the oblique OBC restart variables
at north-south or east-west faces.  Before this fix, some of the full 3-d arrays
for restarts were being overwritten for oblique OBC segments that join at
adjacent corners on the north-east side of tracer points, as is noted in
github.com/NOAA-GFDL/issues/208.  The discussion surrounding this issue
confirms that there are cases using oblique OBCs (like some North-West Atlantic
cases) that do not past the restart reproducibility tests.  Some halo updates
were also corrected, in accordance with the introduction of these new variables
and their proper staggering locations.  In a number of places, the proper
case-sensitive horizontal indexing convention, as described in
github.com/NOAA-GFDL/MOM6/wiki/Code-style-guide#soft-case-convention, is now
being used.  This commit also corrected the comments describing a number of the
variables in the OBC_segment_type to make it clearer where they are discretized.

  This changes the names of oblique OBC-related variables in the restart files,
but since the previous version did not reproduce across restarts, there does not
seem to be any point in retaining those incorrect answers.  All answers in the
MOM6-examples test suite are bitwise identical, but this will change (fix)
solutions with oblique OBCs and OBC_RAD_VEL_WT < 1.