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/gui/SettingsView.qml

@@ -0,0 +1,8 @@
+import QtQuick 2.9
+Rectangle {
+    id: settingsPage
+    color: "#333333"
+    objectName: "Settings"
+
+    // TODO - add settings
+}