Bala2 and Mullein

Copperbox revision 764.

I've added a module to Bala for rhythmic patterns and a 'collective import' module for LilyPond to Mullein.

Unfortunately the RhythmPattern module doesn't really live up to the comment I made yesterday about making Bala stringent. The main datatype just captures the onsets of the rhythm which is fine (this is in accordance with definitions elsewhere), but the interpretation function needs duration as well - a scored rhythm might subdivide an onset with a note an a rest rather than a long sustained note. Currently how I handle this is unsatisfactory.


Copperbox revision 765.

Added a collective import module for ABC to Mullein.