remove bar-size and replace its usage by bar-extent (issue4025044)

[benko . pal]

Reviewers: ,

Message:
patchset related to
http://code.google.com/p/lilypond/issues/detail?id=1268
as outlined in
http://lists.gnu.org/archive/html/lilypond-devel/2011-01/msg00225.html

note that this is the first time I touch Python (for sure) and the
documentation (possibly).

Description:
remove bar-size and replace its usage by bar-extent

Please review this at http://codereview.appspot.com/4025044/

Affected files:
  M Documentation/de/notation/percussion.itely
  M Documentation/es/notation/percussion.itely
  M Documentation/fr/notation/chords.itely
  M Documentation/notation/percussion.itely
  M Documentation/snippets/adding-bar-lines-to-chordnames-context.ly
  M Documentation/snippets/adding-drum-parts.ly
  M Documentation/snippets/ancient-fonts.ly
  M input/regression/drums.ly
  M input/regression/grid-lines.ly
  M input/regression/lyrics-bar.ly
  M lily/bar-line.cc
  M lily/include/bar-line.hh
  M lily/include/span-bar.hh
  M lily/span-bar.cc
  M ly/engraver-init.ly
  M python/convertrules.py
  M scm/define-grob-properties.scm
  M scm/define-grobs.scm