Upload tags

add an option to add an upload tag for each upload task in subatomic, and when you upload with --prune with the same tag, all the previous packages in the same tag gets removed entirely at the same time, this should help when a package update obsoletes older packages, since subatomic currently only removes invididual packages with the same name on --prune, but what we want is to remove all artifacts from that build entirely.

This should work as a stop-gap solution for batch package removals and obsoletes at least until subatomic-ng is done. Requires a new database table to manage all of this