Add delete link to Special:Listfiles

The rationale is that the presence of a delete link can make combating
image upload vandalism substantially easier.

The change was originally added in https://github.com/Wikia/app/pull/3859
and is awaiting merger there.

Change-Id: I94b1a2d551093a4ada7aede1ad5af2a23bf86308
Merge "Add delete link to Special:Listfiles"