Lots of work around artifacts.
Upgraded to using s-ramp 0.1.0. Made the commands cancelable in the hope that the GUI could also use them.
Created a relationship on VdbArtifact so that it knows what its derived artifacts are. Refactored relationship
definitions to their specific artifact type.
Merge pull request #89 from elvisisking/artifact-command-sramp

Upgraded to S-RAMP 0.1.0. Created new artifact types for VDB objects. Made commands cancelable. Worked related to artifact relationships.