PATCHES: drawing notice to quarter-note accidentals

[Graham Percival]

We're down to 1 patch in the "patch-review" category.  It's a
relatively big one, and no programmers have looked at it yet, so I'm
not putting it on a countdown yet.

Issue 1278: Arrow notation for quarter-tones.
http://codereview.appspot.com/3789044/


This patch changes a *lot* of files, but most of them are really
trivial changes like
- stringTunings = #`(,(ly:make-pitch 1 3 0)
+ stringTunings = #`(,(ly:make-pitch 1 3 NATURAL)

That said, there are some significant changes to our architecture.
Felipe has been very patient and careful in making drafts of this
patch; please review.

Cheers,
- Graham