Remove head- and foot-separation. (issue3199041)

[markpolesky]

Reviewers: ,

Message:
If I understand correctly, head-separation and
foot-separation are gone.  This patch just removes the
vestiges from scm/ and ly/, but I suppose we should provide
a convert-ly rule?

So, in an earlier patch by Alexander...
http://codereview.appspot.com/1710046/diff/19001/Documentation/notation/spacing.itely
...he suggests that (using the updated names),
  head-separation = #x
should become
  top-system-spacing #'padding = #x

and that
  foot-separation = #x
should become
  last-bottom-spacing #'padding = #x

Is that precisely how the conversion should be made?  Can
someone verify this?  Should I push this patch or wait for
a convert-ly rule?

Thanks.
- Mark

Description:
Remove head- and foot-separation.

Please review this at http://codereview.appspot.com/3199041/

Affected files:
  M Documentation/notation/spacing.itely
  M input/regression/page-layout.ly
  M input/regression/paper-default-margins-a6.ly
  M input/regression/paper-default-margins-def.ly
  M ly/paper-defaults-init.ly
  M scm/paper.scm