Initial support for physical joysticks

This has been only tested on the Wikipad, but it's a pretty bog standard game controller. I haven't simulated non-springloadedness on the throttle yet. In the software joystick it's implemented using up and down events and the yAxisAutoReturnToCenter parameter. The main problem is that the joystick MotionEvents always show up as ACTION_MOVE. There is no ACTION_UP or ACTION_DOWN for obvious reasons. Maybe a good solution is to increase or decrease throttle in proportion to the current physical throttle position, but I think this requires addition of a timer.