Batch all supplementary information in Diffusion browse views

Summary: Ref T2683. Instead of sending one request for each path's history, send one request for all of it. This permits optimizations which are not currently available to us. It degrades the user experience a tiny bit in theory, but on my machine it's actually way faster already.

Test Plan: Loaded a browse page.

Reviewers: vrana, btrahan

Reviewed By: btrahan

Subscribers: epriestley, aran

Maniphest Tasks: T2683

Differential Revision: https://secure.phabricator.com/D5254