Automate updating of firmware version strings

See merge request !14

It turns out that the underlying problem was that the sensor sends
the number of modes minus one and the code here did not account for it.

Major update of menu visuals and example programs

See merge request !12

This should resolve some licensing ambiguities - previously the code
had no license at all.

I am not entirely comfortable releasing the code under MIT (e.g. it can
then be used by a third-party vendor without giving any code back), but
MicroPython is under the same license and I want to keep the spirit
of that.