GDP: new @lilypond[] options

[Graham Percival]

Thanks to Joe and John, we can simplify the .itely files.  Here's
the new policy:  (from writing-texinfo.txt)

* Most LilyPond input should be produced with:
    @lilypond[verbatim,quote,relative=2]
  or
    @lilypond[verbatim,quote,relative=1]

  If you want to use \layout{} or define variables, use
    @lilypond[verbatim,quote]

  In rare cases, other options may be used (or omitted), but ask
first.

There's no urgency for updating the options, but they should be done
before GDP is over.


If you want to look at pitches.itely, be aware that the first two
examples, and one subsection in the middle, fall under the
category of "rare cases".  :)

Cheers,
- Graham