Replace Sentry with Crashlytics

lib/pages/main.page.dart

@@ -131,6 +131,7 @@ class _MainPageState extends State<MainPage> with WidgetsBindingObserver, Ticker
       }
     });
     eventBus.fire(RefreshDataFinishedEvent());
+    throw new Exception("There is an error thrown specifically for Crashlitycs reporting test!");
   }
 
   @override