Convert Differential to new layout

Summary:
First pass at converting Differential, I likely have some buggy-poos but thought I'd toss this up now in case very bad bugs present.

To do:

• Need to put status back on Hovercards
• "Diff Detail" probably needs a better design

Test Plan: Looking at lots of diffs, admittedly I dont have harbormaster, etc, running locally. Checked Diffusion for Table of Content changes on small and large commits.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D15463