Phriction Documents can be moved

Summary: Refs T1575

Test Plan:
created plenty of pages, did all kind of stuff with them, moved them around, verified expected behaviour.

{F34453}

{F34455}

Reviewers: epriestley, chad, btrahan

Reviewed By: epriestley

CC: aran, epriestley, Korvin

Maniphest Tasks: T1575

Differential Revision: https://secure.phabricator.com/D5198