Add comments, blogs, images etc. to ACP filters

Really, this idea seems pretty pointless, but I can think of one key reason why something like this is necessary. I know some people like to prune their members regularly. If a member hasn't made any posts and hasn't visited in x days then they get pruned. That kind of thing. However, what if that member submitted a comment, or a gallery image? That content gets guestified, but they could've been protected from the pruning if that had been added as an ACP filter.

Regardless, in 4.0 if you can have a standalone gallery then that kind of filter is pretty necessary then.