R1:d9bb66f610db

Update Differential edit pages to new UI

Summary: Updates using PHUITwoColumnView, new headers, etc.

Test Plan: New Diff, Update Diff, View Standalone pages, Edit pages.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D15549