Android: Overhaul the orientation lock setting

When using motion controls, it's useful to be able to lock the screen
to a certain orientation so that Android won't interpret game motions
as an intent to change the screen orientation. To this end, I've
changed the existing orientation lock setting in the following ways:

- A portrait lock mode has been added in addition to the existing
  landscape lock mode and unlocked mode.
- The landscape lock mode now locks to regular landscape rather than
  letting you change between the two possible landscape orientations.
- The setting is now accessed during emulation rather than outside.

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

@@ -313,6 +313,7 @@
     <string name="emulation_ir_group">Touch IR Pointer</string>
     <string name="emulation_ir_sensitivity">IR Sensitivity</string>
     <string name="emulation_choose_doubletap">Double tap button</string>
+    <string name="emulation_screen_orientation">Screen Orientation</string>
 
     <!-- GC Adapter Menu-->
     <string name="gc_adapter_rumble">Enable Vibration</string>