* lily/include/music-output.hh (process): Change signature to

* lily/include/music-output.hh (process): Change signature to
return SCM.

* lily/paper-book.cc (classic_output, get_title, get_scopes): New
method.

* lily/paper-score.cc (process): Return stencils rather than
outputting directly.  Remove paper-book kludge.  Delete grobs.
(output): Remove.

* lily/include/paper-score.hh (class Paper_score): Remove outputter_.

* lily/score-engraver.cc (get_output): Do not reset pscore_.

* lily/score.cc (default_rendering)
(ly_render_output): Move adding paper-score two levels up.