Documentation guidelines

[Fieck, Brennan]

There's a lot of inconsistency in the formatting of the documentation, and 
while (most of) that is being overhauled, it's worth thinking about how to 
prevent things from getting this bad again. I don't know if there are any 
existing guidelines for documentation structure, but if there are they are too 
hard to find. I'd be happy to throw together a draft if everyone thinks that's 
a good idea/worthwhile.