Bug 1073: Introduced Transaction Chain to DOMStore APIs.

Introduced concept of TransactionChain to DOMStore APIs.
Decomposed DOMStore to DOMStoreTransactionFactory
to allow factory methods reuse between DOMStoreTransactionChain
and DOMStore itself.

Change-Id: I186242e40e8ada098deb431b09db67707371af58
Signed-off-by: Tony Tkacik <ttkacik@cisco.com>
Merge "Bug 1073: Introduced Transaction Chain to DOMStore APIs."