Minor enhancements for the countdown face (#177)

Minor enhancements for the countdown face (#177)

* minor enhancements for the countdown face

* Changed usage of countdown timer.

- Long button presses have been removed.

- The light button is used to restore the last countdown as well as enter setting mode when pressed again.

- The visual state has been removed from the display.

- The internal states have been renamed to reflect the new logic.

* restore time when countdown finished.

* support for fast forward on long press (untested).

* support for beeps similar to stop watch

* fixed bug wiht display when fast forwarding