[Denemo-devel] LilyPond text editing

[Richard Shann]

I've checked in this work now. In the LilyPond text window you can
customize everything except the notes, which remain editable in Denemo.
Moreover, the output from the LilyPond typesetting process is captured
and displayed in the case of errors or warnings.
The cursor places itself on any LilyPond error and the error text is
highlighted (give or take some minor problems that gtk still has with
invisible text). 
Moving the cursor over text in the LilyPond window finds that object in
the Denemo window - even switching movements if needed.
And conversely you can use the right-click menu in the LilyPond text
window to find the text for the current object. 

In addition there are some general improvements. I've added the
possibility of splitting off and merging back a polyphonic voice - this
makes it easier to write the voices, and I've made the yellow color
darker so that it is more easily seen. We still need something to toggle
the non-printing attribute of rests off and on, at the moment you have
to delete and insert.

Richard