Fix various wording, punctuation, and capitalization issues
This merge request fixes a lot of wording, punctuation, and capitalizations issues, mostly focusing on the blending mode pages. They're still not perfect: Most notably I'm not fully sure what the descriptions for Darken/Lighten, Fog Darken/Lighten, Pin Light, and Shade are trying to say, so they're still a bit mangled.
Edited by R. B.