Added a Gamepad device interface for the Pandora

|SOURCE|
[Common/Gamepad]
* The Gamepad is specifically targetting the Pandora, this will most likely be
  a separate gamepad device later
* The left pad's up button (up on the Pandora's D-Pad) is the only button
  returned when pressed
* Analogue data is collected, but has not yet been tested
[Common/Game]
* Removed the temporary test code for the input device acquisition
* Using a Gamepad object and checking for the Pandora's D-Pad Up key being
  pressed to quit the game
[Common/InputDevice]
* An abstract interface for real input devices to derive from