initial working connection of an xbox gamepad
move JoystickManager to JoystickScriptingInterface, add Joystick class for SDL Joystick
add a property for number of buttons in Joystick
report the 360 axis values in xbox.js
map PrioVR to new JoystickScriptingInterface
change name in header comment to match new class name
add a missing HAVE_SDL block
Merge pull request #3476 from birarda/xbox-controller

add script support for general SDL controllers