correct numerous errors in documentation

I am working on an automated way to compare the signature of functions and their documentation in #1196. I have a draft of that working locally, but with too many false positives for now. However, in an attempt to get the most important documentation fixes in before 0.4.0, I have hand sifted through the differences and tried to fix those I could.
In general, I tried to make the documentation match the code (assuming that the code is what has been modified last), but please look through and check.

@taldcroft @astrofrog @embray @mdboom @eteq
(and probably other people whose modules I have changed but whose alias I don't know)