R1:9a9df74ddb34

Minor documentation improvements

Summary: Tidying up of documentation, adding some new groups.

Test Plan: Eyeball it.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D13133