Show image dimensions and some other metadata in Differential

Summary: Fixes T2101. When viewing an image change, show image dimensions, MIME type, and filesize.

Test Plan:

very utility

such wow

Reviewers: mailson, btrahan, chad

Reviewed By: chad

Subscribers: epriestley, Korvin, aran

Maniphest Tasks: T2101

Differential Revision: https://secure.phabricator.com/D5206