upgrade diffusion to use modern header UI and fix a few quirks

Summary:
upgrades are CrumbsView, HeaderView, PropertyListView, and ActionListView. I had to modify CrumbsView stuff a bit to handle the "advanced" diffusion crumbs.

Quirks fixed include making file tree view show up in diffusion, the page not have extra space when the file tree is hidden, links no longer breaking once you visit files (since without the change the files always got "/" appended and thus 404'd), and a differential quirk where it read "next step:" and that colon is a no no,

Test Plan: played around in diffusion and differential

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin, chad

Maniphest Tasks: T2048, T2178

Differential Revision: https://secure.phabricator.com/D4169