Stretch menu background configuration more accessible

Stretch menu background setting needs to be easier to find. It is quite important since, by default on widescreen monitor when using any widescreen menu texture and splashscreens, they will be shrunk to 4:3 aspect ratio. That confuses a lot of new people and most of them wouln't think of fiddling with the settings that can't be changed in the launcher or ingame configuration menu.

I believe it fits the most appropriately to launcher.