TODO

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