Add MidiFileIn.py with experimental midi playback
multi channel midi playback from file is now working

- there are still a few issues when changing tempo during playback
- untested on Floppies yet
moved frequency test to settings > benchmark window
- Added experimental midi file playback to FlyFi
- Moved floppy frequency tester to benchmark tab in SettingsWindow.py
- Added buttons for benchmarking notes (not implemented yet!)
Merge branch 'file_reader' of https://github.com/XenGi/FlyFi
fixed an evil bug which slowed down midifile playback on complex files