Transferring these files into their own repository. These files make up
the song generation engine. I should be able to export this as a library
so it can be used other places. Other proojects then can focus more on
creating a front end for this song-generation backend.
Rename MidiManager to MidiGenerator to more accurately reflect its
functionality

Also removed an instrument that I didn't like.
Do some renaming from SongGeneration to SongBuilder. This helps
distinguish this project/library from the projects that use it
(currently called SongGenerator)