[Denemo-devel] Checked in improvements to LilyPond text

[Richard Shann]

It was difficult to read the LilyPond identifiers which use Roman
numerals I, II, III etc in the default sanserif typeface, and the
LilyPond text, being code needs to be monospaced. So I have monospaced
the code & the labels.
In addition I have made the colors better (gray for the insertion points
and a lighter highlighting for errors).
Checked in.
Richard