Some violin sound file fixes and a converter for MIDIs -> piano/violin format

- I don't know why I just noticed, but whoever originally made the violin midis accidentally transposed all of the A and B notes down an octave such that all properly written music was wonky on those notes (piano notes have always been correct in this regard).

- I also added an updated version of an old MIDI -> piano/violin format converter I made, especially considering I'm not sure if it's still easily findable; the old version posted also had a few bugs and did not have released source.

- Also removed redundant sound files, such as the sharps and the Cb, B#, Fb, and E#, cleaned up playnote() to be more maintainable, so no-one has to go through 200 lines to fix basic file formatting changes.