Return tombstones (Vclock) so a K/V can be rewritten directly after a delete

When an object is deleted it may take some time before it is really successfully removed from all replicas. By GETting an object before storing it and setting the Vclock correctly new objects can be written without them getting lost or creating siblings.
Merge pull request #43 from tpjg/deletes

Return tombstones (Vclock) so a K/V can be rewritten directly after a de...