Improve some setting descriptions in the graphics options.

More than a few of these have annoyed me for a while, what with their typos and odd wording and occasional lack of important details.

Criticisms welcome. I mean, as long as it doesn't devolve into MORE bikeshedding. Even I don't enjoy that.
I think it would be good to say that the software render shouldn't be used because it's very slow. Not everyone knows what debugging is, the word debugging can be hard to localize, and the current text doesn't explain _why_ the software renderer only is used for debugging.