TODO

   1
   2 ptb2xml:
   3  - convert to UTF-8 before calling libxml
   4
   5 finish ptb2musicxml
   6
   7 ptb2ly:
   8  - 8VA, 15MA, etc
   9  - dynamics
  10  - floatingtext
  11  - tempomarker
  12  - chorddiagram
  13  - finish chordtext
  14
  15 ideas:
  16 ptb2gp and gp2ptb conversion utilities