Bug Fix: Voices now allocated in the correct order.

Not only are voices now allocated in the order
given in the .mkss settings file, but midi channel
allocation has finally been cleaned up:
Algorithms never allocate midi channels to voices.
Voices are printed in the order given in the score's
.mkss file, and midi channels are always allocated
(only to output voices) in ascending order from
top to bottom in the score (i.e. the top voice always
has midi channel 0).
Refactored all the names that referred to midi
channels where output voice indices were meant.
Bug Fix: Study 3 sketch 2 now compiles correctly.

VoiceDefs were being allocated incorrectly in
ComposableScore.CreateEmptySystems.