Clarify InputDevice#getControllerNumber documentation

    /**

     * The controller number for a given input device.

     * <p>

     * Each game controller or joystick is given a unique controller number when initially

     * configured by the system. The number is not stable and may be changed by the system at any

     * point.  All controller numbers will be non-negative. A game controller or joystick will be

     * given a unique number indexed from one; everything else will be assigned a controller number

     * Each gamepad or joystick is given a unique, positive controller number when initially

     * configured by the system. This number may change due to events such as device disconnects /

     * reconnects or user initiated reassignment. Any change in number will trigger an event that

     * can be observed by registering an {@link InputManager.InputDeviceListener}.

     * </p>

     * <p>

     * All input devices which are not gamepads or joysticks will be assigned a controller number

     * of 0.

     * </p>

     *

     * @return The controller number of the device.

     */

    public int getControllerNumber() {

        return mControllerNumber;