ImageReviewTask migration

@Wikia/platform-team 
migrating over ImageReviewTask to modern job queue system.
Nah, Special:Tasks shows tasks in the same directory as MathTask, or tasks that get in via hook. I definitely don't want all tasks to live in this namespace, but the original ImageReviewTask has the same name. My plan is to change this back to the global namespace when we git rm the old one.