added location overview screen

lib/pages/task_overview_page.dart

@@ -6,6 +6,7 @@ import '../model/task.dart';
 import '../service/controllers/task_controller.dart';
 import '../service/tools.dart';
 import '../widgets/task_dismissible.dart';
+import 'locations_overview_page.dart';
 import 'task_edit_page.dart';
 
 class TaskOverviewPage extends StatefulWidget {
@@ -22,7 +23,20 @@ class _TaskOverviewPageState extends State<TaskOverviewPage> {
   @override
   Widget build(BuildContext context) {
     return Scaffold(
-      appBar: AppBar(title: Text('Hallo Yannick')),
+      appBar: AppBar(
+        title: Text('Hallo Yannick'),
+        actions: [
+          PopupMenuButton(
+            itemBuilder: (_) => [
+              PopupMenuItem(
+                onTap: onLocationsButtonTapped,
+                child: Text('Locations'),
+              ),
+            ],
+            icon: Icon(Icons.more_vert),
+          ),
+        ],
+      ),
       body: Padding(
         padding: EdgeInsetsGeometry.symmetric(
           horizontal: MediaQuery.of(context).size.width * 0.05,
@@ -84,10 +98,13 @@ class _TaskOverviewPageState extends State<TaskOverviewPage> {
         await Navigator.of(context).pushNamed(TaskEditPage.routeName)
             as CreateTaskRequest?;
 
-    if (result != null && context.mounted) {
+    if (result != null && mounted) {
       context.controller<TaskController>().saveTask(
         result.toTask(id: generateId()),
       );
     }
   }
+
+  void onLocationsButtonTapped() =>
+      Navigator.of(context).pushNamed(LocationsOverviewPage.routeName);
 }