TentativeGenerationNumber

During a replicated transaction, the GenerationNumber representing the new "candidate" revision of an object.

If the transaction succeeds, the TentativeGenerationNumber will become the new CommittedGenerationNumber for the object.
In order to cope gracefully with weird transport artifacts, each TentativeGenerationNumber will have associated with it the ID of the originating ZEOStorageServer? (the ReplicationCoordinator).