pl 21:
	- Move breaking stuff into a separate class Break_algorithm
	- dependencies for Staff_elem's
	- scripts
	- texts
	- nplets (triplets!)

pl 20:
	- Rational for time measurement
	- updated doco to .pod
	- directionalspanner/textspanner
	- include files

pl 19:
	- struct Moment
	- grouping code: LilyPond can set advanced multibeams.

pl 18:
	- robust Staff_commands

pl 17:
	- robust Input_commands
	- merged Vertical_/Horizontal music
	- PARTIALs with duration
	- modularized lexer: multiple runs

pl 16
	- notenames configurable

pl 15
	- grouping code
	- multibeams (simple)

pl 14
	- symtables from .ly
	- Input_command
	- Input_{score/staff}

pl 13
	- Horizontal/Vertical music
	- Input_commands