Increase the maximum size eligible for image transforms configurable from 4MB->16MB
Summary: Also increase the timeout for the external process to complete the transform.
Test Plan: Careful inspection
Reviewers: epriestley, #blessed_reviewers
Reviewed By: epriestley, #blessed_reviewers
Subscribers: joshuaspence, cburroughs, chad, Korvin
Differential Revision: https://secure.phabricator.com/D14528