Add video driver selection to settings menu (based uppon idea from webde...

...signer97)
A enum order is always defined starting at 0 if not specified different. In case irrlicht changes this we will have to change it anyway. So unless you have a better suggestion I'll not change it.
And exploding ... of course if irrlicht adds more driver we will have to support more of those I don't recognize any other way to do.