[Bug 1074943] User create, detail, and create APIs

This is an unauthenticated API to create users (and profiles). It treats Users and Profiles as a single combined object, and not as separate things. It also has an API for listing users and getting details on them. This lacks much of the data in our profiles (like Twitter handle, bio, or avatar), I'll add those later.

This doesn't have any ability to delete users or modify them, for any users.

r?
I see email is write_only as well. Is that necessary in all cases? How can we show them their email on the edit profile screen, for example?