0.4.1: Graphics settings

I’ve added graphics presets to the pause and main menu. Nothing much, but it should help with lower-end PCs. I also fixed a few things like the default contrast/brightness settings if you’re playing for the first time, things floating in air, and so on.

One caveat: selecting “Minimal” if you run with with the --rendering-method gl_compatibility parameter may result in fog effectively blanking the terrain. This only occurred on my potato laptop, and the “Low” setting doesn’t appear to be affected.