support unregistering typewriter button updaters
react to octave change in typewriter
support octave selection in typewriter manager
implement octave selector
make get_closest_keymap_pitch work with low pitches
add a getter for selected octave
use toggle buttons for octave selection
add leds to octave buttons
implement get_pitches_by_octave
update octave button leds
Merge pull request #85 from cyberixae/implement_octave_selector

Implement octave selector
Fix event buffer add counter usage.
Test location query event at the initial location.
Support location query event.
Test location query at the end of a track.
Test voice count query event.
Implement voice count query event.
Test force query event.
Support simple force adjustment in the debug generator.
Update actual note force in .f event for force query purposes.