Add a UI element for navigating between versions of a Phriction document

Summary: Depends on D19621. Ref T13077. Fixes T4815. This adds previous/current/next/draft buttons and makes navigation between unpublished and published versions of a document more clear.

Test Plan: {F5841997}

Reviewers: amckinley

Maniphest Tasks: T13077, T4815

Differential Revision: https://secure.phabricator.com/D19622