Android: Add default touch button overlay

This sets up default positions for touch buttons so they are not just bunched in the corner on a fresh install. Also added a toast when emulation starts on how to edit button layout

Source/Android/app/src/main/res/values/strings.xml

@@ -269,6 +269,7 @@
     <string name="emulation_control_joystick_rel_center">Relative Stick Center</string>
     <string name="emulation_choose_controller">Choose Controller</string>
     <string name="emulation_controller_changed">You may have to reload the game after changing extensions.</string>
+    <string name="emulation_touch_button_help">To change the button layout, open the menu -> Configure Controls -> Edit Layout</string>
 
     <!-- GC Adapter Menu-->
     <string name="gc_adapter_rumble">Enable Vibration</string>