Add button combos to reverse axis on analog sticks

[Konsolkongen]

A lot of sixth generation games use weird camera controls where the x-axis is reversed, making them hard to play.

I know that we can reconfigure the button mapping in the webui, but some button combo on the controller itself that could swap left and right on the fly would make this a lot easier.

Ideally there would be combos to reverse any axis on both sticks, but the right stick would be the most useful.