Added functionality for noteFromMidiPitch

Added function to return Midi note from pitch. Rearranged exports mechanism. Added a test script to output all notes for pitches from 21 to 108.
Perhaps reword to `Use flattened notes if requested (e.g. f# should be output as gb)`.

It would be fun to (in future!) accept an optional key signature, and name the notes according to that key. For example, passing a key signature of `e` would give you `d#` for the pitch, but a key signature of `cm` would give you `eb` instead.