PartListingViewController replaces HomeMenuViewController.
It has a list of PartListingCells and a New button. Files in the listing are sorted by date modified in decreasing order, so that most recently modified comes first. Click on a part to open it, and any changes are saved to that part.
Other changes:
MusicXMLParser has all static functions bc it only translates between formats, so it shouldn't have state
PartFileManager handles saving and loading parts by filename
PartSaver is a PartStoreObserver that saves a part to a file after every change
closes #263
PartListingViewController replaces HomeMenuViewController. It has a list of PartListingCells and a New button. Files in the listing are sorted by date modified in decreasing order, so that most recently modified comes first. Click on a part to open it, and any changes are saved to that part.
Other changes: