AddVlanBean now properly manages the conversation
introduce the SaveableVlanEditor

This was introduced so that the editor can be responsible for saving
itself.  It's on a different interface, so that we don't expose the
"save-ability" to the web tier user of the VlanEditor interface.
introduced VlanEditorFactory

We want concrete editor creation to be central, so we'll use an instance
of this interface as a delegate for AddVlanService.createEditor
introduced AddVlanServiceBean and test suite

The tests are fleshed out based on our understanding of the public API
of the bean and its interactions with its collaborators
(subcontractors), but the methods of the bean are not yet implemented
(i.e. test first).
implemented the public methods of AddVlanServiceBean