Re: renaming "vertical spacing inside systems" props

[Mark Polesky]

Keith E OHara wrote:
> We will use this in context that makes that first
> qualifier almost redundant :
> \override Context.StaffGrouper #'withingroup-staff-staff-spacing

This is an excellent point, and in response I'd like to
propose one more option -- just remove the "withingroup"
prefix altogether:

  \override StaffGrouper #'staff-staff-spacing
  \override StaffGrouper #'staffgroup-staff-spacing

Yes, I know we already have a 'staff-staff-spacing for the
VerticalAxisGroup grob, but there's no law saying we can't
have a different property with the same name for the
StaffGrouper grob.  We already do that in several other
cases, for example:

  \override Beam #'details = ...
  \override Stem #'details = ...

Similarly, I think the two 'staff-staff-spacing properties
would be intuitive and easy enough to keep separate,
mentally:

  % space between consecutive staves in a system
  \override VerticalAxisGroup #'staff-staff-spacing

  % space between consecutive staves in a staff-group
  \override StaffGrouper #'staff-staff-spacing

The property descriptions could have a brief mention to
dispel any confusion, and then we won't need any awkward and
long "withingroup" prefix.  And best of all, the name is
consistent with the "item1-item2-spacing" format.  I think
it's elegant.

Thoughts?
- Mark