This eliminates datastore-internal TransactionIdentifier in favor of the
concept one, which is structured. Since the structured identifier also
includes LocalHistoryIdentifier, this eliminates also ChainedTransactionIdentifier.
Change-Id: Iabfa2ddd7aadd1e4913115f342e520ffaa8b84f0 Signed-off-by: Robert Varga <rovarga@cisco.com>