Better support for MIDI file playback

[achimmihca]

Actual behaviour

The support for MIDI files is limited due to bugs and limitations of the used library.
This means not every standards complient MIDI file will work in the game.

Expected behaviour

Would be nice to have full MIDI that can handle every standards compliant MIDI file.

Implementation

Currently, the game uses a custom fork of CSharpSynthForUnity2.0

Instead, it might be possible to port a more complete MIDI implementation to Unity, e.g., meltysynth or TiMidity from SDL library.