HNotate

Copperbox revision 241.

HNotate alt - I've added extracting parsers for LilyPond and Abc.

Extracting parsers are island parsers that parse a file and extract some facts but leave much of the content uninterpreted. As they are much simpler than a full parser, hopefully they will always succeed rather than throw a parse error.

My current thinking is that output from HNotate should be limited to just note sequences (after all the input is a just a note list). Larger structure - multiple staffs, headers, and the like - should be specified in LilyPond or Abc files where it can be done more conveniently. Meta-comments in the LilyPond or Abc files can indicate template holes where HNotate will output note sequences.