Made most of People inaccessible for passer-bys

Summary:
Depends on D5360; Refs T2770

See https://secure.phabricator.com/chatlog/channel/6/?at=54481 for discussion.

This will be a sad day, when I will repeatedly continue to hit a glass wall trying to get into `/people/` to browse the user list J4F at http://secure.phabricator.com/.

Test Plan:
verified that I could not access People as some passer-by.

Verified I could still access user profiles (at least I think I got the right controller for that).

Reviewers: epriestley, chad, btrahan

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2770

Differential Revision: https://secure.phabricator.com/D5386