Timer App (#355)

* built timer app

* Style improvements

* making sure buttons stay hidden when the app is reopened and reappear after the timer runs out

* more sensible calculations of time deltas. eliminated that mysterious scaling factor

* changing the timer icon

src/components/motor/MotorController.cpp

@@ -13,7 +13,6 @@ MotorController::MotorController(Controllers::Settings& settingsController) : se
 void MotorController::Init() {
   nrf_gpio_cfg_output(pinMotor);
   nrf_gpio_pin_set(pinMotor);
-  app_timer_init();
   app_timer_create(&vibTimer, APP_TIMER_MODE_SINGLE_SHOT, vibrate);
 }