Update some setting descriptions in the graphics options. Hide "Disable Destination Alpha" from wx UI.

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.
Is it in any way actually relevant that D3D has a special behavior here? I mean, I get that it might be surprising for some people, but it's not really important at all and given that the point of these descriptions is to give the user some idea of what this stuff is doing, this seems rather overcomplicating than anything else.