Add navigation toolbar (#1)

* Add preferences view skeleton

* Add toolbar & help button

* Add working back button

* Title of page in toolbar

* Remove unused imports

* Make comments better!

* Remove unused drawer element

* Remove superfluous > 1 check

* Use point size font instead of pixel size

* Add AppView page title

app/qml.qrc

@@ -6,5 +6,6 @@
         <file>gui/ic_tv_white_48px.svg</file>
         <file>gui/ic_add_to_queue_white_48px.svg</file>
         <file>gui/AppView.qml</file>
+        <file>gui/SettingsView.qml</file>
     </qresource>
 </RCC>