Add Document PropertyList item to LegalPad

Summary: Makes Legalpad a little easier to grok.

Test Plan: View Document

Reviewers: epriestley, btrahan

Reviewed By: btrahan

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D7460
Merge branch 'master' of http://github.com/facebook/phabricator