UI fixes (back arrow, blue switch bar, append whether Talkback is on to

summary), Talkback no longer disabled when preference is tapped, fixes
SettingsPreferenceFragment to not check parent class to determine whether to
show options menu.

Change-Id: I3345e1a878f51b4387ca1bfe89855339617a94d6

res/xml/accessibility_settings_for_setup_wizard.xml

@@ -42,7 +42,7 @@
 
     <Preference
         android:key="talkback_preference"
-        android:summary="@string/talkback_summary"
+        android:title="@string/talkback_title"
         android:persistent="true" />
 
 </PreferenceScreen>