Always pull extra browse information over Ajax, and batch some of the queries

Summary:
This code is currently quite complicated because we pull history data inline for SVN files, and via ajax for everything else (SVN dirs, everything in Git and Hg).

Always pull over ajax; batch some of the queries.

Test Plan: {F34860}

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley, vrana, aran

Maniphest Tasks: T2683

Differential Revision: https://secure.phabricator.com/D5255