Add tombstone for move

We want to avoid dealing directly with JCR nodes at the fcrepo-http-api level. 
Additionally, if the request to move a resource comes directly against the NodeService, we also want a tombstone to be created, i.e. tombstones are not something that only need to be created when a invocation comes through the REST-API.
I would suggest moving the tombstone creation logic into NodeService.moveObject().