After a bit of testing I have not yet come up with a fast, visually
acceptable horizontal animated effect. Instead we simply reply on
screen blanking during the redraw... meaning there is no need for an
effect hint.
This is a big change that break compatiblity with existing applications
*and* with existing installed versions of main.py.
When upgrading it is import to update main.py:
./tools/wasptool --upload wasp/main.py
Moving it from applications into the watch is useful for two reasons.
Firstly it means applications don't need to know as much about the
display color depth and secondly it makes it easier to replace the
drawing routines with wasptool.
