[Android] Refactor InputConfigFragment a little bit in preparation for the implementation of the new input overlay.

This moves all of the dialog handling into the actual MotionAlertDialog class itself. This is something I should have done a long time ago.
Also moved the Gamecube input binding preferences into their own PreferenceScreen.

Source/Android/res/values/strings.xml

@@ -41,6 +41,7 @@
 
     <!-- Input Config Fragment -->
     <string name="input_settings">Input</string>
+    <string name="gamecube_bindings">Gamecube Input Bindings</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>