Feature Request: Image Sets

[coreyopsis]

Some of the images I have saved are part of a set, like comic pages, separated tutorial images, or alternate versions of an image with minor edits. In these cases, I think it'd be useful to be able to collapse these into a set, so they can be more easily associated with each other. My current solution has been to have a new tag for each set, which is clunky. It might also be useful to have an option to collapse them into one preview tile when searched for.