Update documentation.

Correctly dereference pointers.

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.