anelok: PIN input demo

[Werner Almesberger]

I made a little video that illustrates how to input a PIN:

http://downloads.qi-hardware.com/people/werner/anelok/tmp/pin-demo.ogg

The PIN is rather simple, "2013". The current code can also use
letters (you get letters when turning right at the "-"), but I'm too
lazy to edit that clip :)

The user experience isn't very friendly yet. The static alphabet at
the bottom doesn't work so well. Perhaps Anelok should instead show
a short moving sequence of surrounding characters.

The movement of the arrow (or character position) could also be made
a bit smoother since I'm currently only using full steps (when the
wheel clicks into a position) and not half-steps (between positions).

- Werner