R1:0271b051aeb5

Modernize Diffusion "history" view

Summary: Fixes T903. Knock out the side nav, make it policy-aware, other minor cleanup.

Test Plan: See below.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T903

Differential Revision: https://secure.phabricator.com/D7064