Neume

Copperbox revision 1156.

I've added a prototype of the new beam algorithm. Because note-lists are now a fairly unwieldy shape to handle tuplets (a forest - i.e. a list of trees), it is not as precise as previous versions of the algorithm - e.g. its possible to have rests ending a beam group in some cases. But I think it is good enough.

Unfortunately the new beaming uses different data types to the CExpr (context expressions) that I had previously implemented so adding beaming fully will mean changing the all the LilyPond and ABC pretty print code.