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

movement/watch_faces/complication/countdown_face.h

@@ -40,9 +40,10 @@ movement_schedule_background_task() while the timer is running.
 
 
 typedef enum {
-    cd_waiting,
+    cd_paused,
     cd_running,
-    cd_setting
+    cd_setting,
+    cd_reset
 } countdown_mode_t;
 
 typedef struct {
@@ -51,6 +52,9 @@ typedef struct {
     uint8_t hours;
     uint8_t minutes;
     uint8_t seconds;
+    uint8_t set_hours;
+    uint8_t set_minutes;
+    uint8_t set_seconds;
     uint8_t selection;
     countdown_mode_t mode;
 } countdown_state_t;