Document why each issue is a problem

[dburgener]

We have the one line descriptions of each issue in the analysis output and the README, and we have (not fully updated) examples in check_examples.txt, but I don't think there's anywhere with more fully fleshed out documentation about why each of these things is bad and what should be done to correct them. Depending on the check (ordering), some more thorough documentation about how it works might also be helpful. The wiki would probably be a good place for this info.