refactor(preload/bhi): Make app more pythonic

This patch makes the BHI160 app more pythonic and fixes a few
bugs/issues:

- An exception (including KeyboardInterrupt) will trigger the sensor to
  be closed again.  Otherwise you'd get strange behavior trying to
  reopen then afterwards.
- Use simple_menu.button_events() instead of home-cooked solution.  This
  should hopefully make the code more future-proof.
- Fix overlapping text caused by the font-rendering changes.

Signed-off-by: Rahix <rahix@rahix.de>