[Android] Expand the input binding UI in the settings to handle 4 Gamecube controllers in the future.

Other changes:

 - Broke out MotionAlertDialog into it's own separate class.
 - Made a preference specifically for handling input bindings.

Source/Android/res/values/strings.xml

@@ -46,6 +46,10 @@
     <string name="input_overlay_layout">Input Overlay Layout</string>
     <string name="input_overlay_layout_desc">Button layout for the input overlay.</string>
     <string name="gamecube_bindings">Gamecube Input Bindings</string>
+    <string name="controller_1">Controller 1</string>
+    <string name="controller_2">Controller 2</string>
+    <string name="controller_3">Controller 3</string>
+    <string name="controller_4">Controller 4</string>
     <string name="input_binding">Input Binding</string>
     <string name="input_binding_descrip">Press or move an input to bind it to %1$s.</string>
     <string name="button_a">Button A</string>