HNotate

Copperbox revision 297.

I've cleaned up the BuildNoteList module - the last one rather complicated, I wrote in a fit of enthusiasm after discovering apomorphisms. The latest one uses a nice new typeclass Fits which might suffer the terrible fate of being used for only one type. If I had of written Fits before the new pretty printer I might have used it in that, but the 'fitting' there is much simpler than for the note list (where none-fitting notes must be split across bars with ties) - putting it in the pretty printer now might actually complicate things.

Thinking about yesterdays comment, I'm changing my opinion and I think I was wrong to 'add context' to the annotations and might remove the Abc / LilyPond differentiation rather than extend it. Apropos the 'canonical notelist' I mentioned, it is quite possible that annotation will be best done as a traversal / transformation over the canonical notelist, with different transformer functions for Abc and LilyPond.