R1:f652123c5a47

Add PhabricatorFactSpec, for naming and formatting facts

Summary: Not totally sure about this but I think it's okay?

Test Plan: Loaded /fact/, got a more readable page.

Reviewers: vrana, btrahan

Reviewed By: vrana

CC: aran

Maniphest Tasks: T1562

Differential Revision: https://secure.phabricator.com/D3090