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/systemtask/SystemTask.h

@@ -16,6 +16,7 @@
 #include "components/ble/NimbleController.h"
 #include "components/ble/NotificationManager.h"
 #include "components/motor/MotorController.h"
+#include "components/timer/TimerController.h"
 #ifdef PINETIME_IS_RECOVERY
   #include "displayapp/DisplayAppRecovery.h"
   #include "displayapp/DummyLittleVgl.h"
@@ -45,6 +46,7 @@ namespace Pinetime {
         TouchWakeUp,
         OnNewTime,
         OnNewNotification,
+        OnTimerDone,
         OnNewCall,
         BleConnected,
         UpdateTimeOut,
@@ -100,6 +102,7 @@ namespace Pinetime {
 
       Pinetime::Controllers::Ble& bleController;
       Pinetime::Controllers::DateTime dateTimeController;
+      Pinetime::Controllers::TimerController timerController;
       QueueHandle_t systemTasksMsgQueue;
       std::atomic<bool> isSleeping {false};
       std::atomic<bool> isGoingToSleep {false};