Remove symlinks and make codebase use common modules instead.

Provide latest versions of the files.

Update documentation.

Provide default states for input and output.

Allow MIDI input to be filtered through MIDI channels.

Restrict Yes/No actions in same 2-octave span.

The file has been updated upon introducing MIDI controller input
support.

Make device handling opt-in.

Ensure that initial loading of the config saves the values back to the
config file, in order to account for fallback values.