Added "Assign to button" option to "User Specific" page.
DO NOT assign directional buttons by clicking the button on screen and press the button on the controller, but you can set other non-directional buttons as usual. You have to assign directional buttons by enter the button number to "Assign to button" field on the "User Specific" page. Those buttons may not react normally on the browser, please test on OBS.
Every time you change the value in "Assign to button" on the "User Specific" page, it may mess up other buttons, so please check all other buttons again afterwards.