Fix 1198: Fix displayLilyMusic for \time and #(set-time-signature) (issue1986042)

[Carl . D . Sorensen]

Reviewers: Neil Puttock,

Message:
I've posted a patch that fixes 1198 so \time and (set-time-signature
will now be displayed properly.

Thanks, Neil for showing how it could be done with ottava.

Please review.

Thanks,

Carl

Description:
Fix 1198: Fix displayLilyMusic for \time and #(set-time-signature)

create TimeSignatureMusic to allow the display to work properly

* scm/define-music-display-methods.scm
  define a display method for TimeSignatureMusic
  remove extra-display-methods for ContextSpeccedMusic and Timing that
  caught \time

* scm/define-music-properties.scm
  define time-signature-arguments as a music property

* scm/define-music-types.scm
  create make-time-signature-set for setting the time signature
  add TimeSignatureMusic

* scm/music-functions.scm
  replace calls to make-beam-rule-time-signature-set with calls
  to make-music 'TimeSignatureMusic

Please review this at http://codereview.appspot.com/1986042/show

Affected files:
  M scm/define-music-display-methods.scm
  M scm/define-music-properties.scm
  M scm/define-music-types.scm
  M scm/music-functions.scm