Document All The Things (At Once)

This should be enough to get us by for now.

I'm going to make it a hard requirement from now on that pull requests contributing significant new functionality come with documentation.
Leaving them unconditionally unavailable is fully equivalent to just removing them outright, except you get to control the error message they get.  :)  I'm not sure how much that buys us, here.  They'll have to update their code no matter which of the two we pick.