This brings this naming into consistency with both fellow consts in the
same file (ex. LeaderMode is singular) as well as the variables in which
the consts are usually used (usually a `Firmware.unicode_mode` attribute
in a keymap).
Resolves#70, Resolves#67
Still needs some regression testing in general, and a definite
regression is that rotary encoders are no longer (for the immediate time
being) supported.
Moves to a much simpler internal state tracking system, and FAR lighter
matrix scan.
Removes MicroPython support entirely.
