curator needs a delete action

curator should have support for deletion of an artifact, even if that artifact is in the handed over state (it would be helpful because then we could delete that one artifact and force another handover). 

I'd like to see something like :

docker run -e SERVER_URL=http://curator-fuse-productization.cloud.paas.psi.redhat.com docker-registry.upshift.redhat.com/fuse-containers/curator-cli:latest update-deliverable --action=delete --release-name fuse-7.9 --milestone-name AR12 --artifact-name atlasmap-2.1.6

This would delete the productization-name/version and artifact-name/version entries for atlasmap-2.1.6.    It should be powerful enough to not care what state the artifact is in (use case here is that we've already handed over, we want to delete one artifact line and then force another handover message)

Bonus points if the CLI asks "Are you sure you want to delete atlasmap-2.1.6? (y/n)" and displays the view-deliverable entry for atlasmap-2.1.6 in 7.9 / AR12 to give more information on what is going to be potentially deleted.