Support QuestyCaptcha and (kind of) MathCaptcha

MathCaptcha just extends SimpleCaptcha, so its output is fine to show as
text. Doing that because I'm not sure how to render TeX and this is a
reasonable fallback

Also tidy up the order of some message entries in my last commit.

Bug: 64328
Change-Id: I98312f61471667e7c4dcf715295f85642c31a688
Merge "Support QuestyCaptcha and (kind of) MathCaptcha"