MCAPP 0.7.1

- Key signature backend interface done - no implementation yet.
- Changed how note pitches work - the Note object stores the _vertical
index of the note_ now, NOT the number of semitones above/below middle
C. This is so it can be used as a lookup by the key signature.
- Moved the grid-to-pitch table into Globals - although it may seem that
it should probably exist in Player, it will be needed in the future for
demoing notes.