Clean up image file diffs UI

Summary: Uses AphrontTable now, cleans up interactions. Fixes T5874, Fixes T4910

Test Plan:
tested a large image

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T4910, T5874

Differential Revision: https://secure.phabricator.com/D10296