R1 L1 for flippers

[kerryland]

I wanted to be able to use a game controller (eg: Playstation 4) with the left and right bumpers to control the flippers. Now I can.

Note:

• Bumping minSdkVersion to 9 was required to access KeyEvent.KEYCODE_BUTTON_L1. This means the app won't run on anything older than Gingerbread devices from about 2010. If that's a problem the keycodes could be replaced with their numeric literals.
• The code that uses KEYCODE_BUTTON_A to start the game is not strictly required by the commit. It's actually a byproduct of removing the "START BUTTON" menu item in Now can see the tables when browsing them #179

[dozingcat]

This is great, thank you! (And sorry for the delay). Works well with my third-party Xbox controller.

I think it will be ok to keep minSdkVersion at 4; my understanding is that because KEYCODE_BUTTON_L1 is a static final field, it gets inlined rather than accessed at runtime.