Bug 499: Initial draft of in-memory datastore and data broker

Initial implementation of InMemoryDOMDataStore with support
for commits to the store and conflict checking

  - DOMDataBrokerImpl - initial implementation of DOM Data Broker which
       uses InMemoryDOMDataStore instances as store for Operational
       and Configuration data

  - InMemoryDOMDataStore - implementation of in-memory DOM Data Store
      which uses MutableDataTree

  - Updated SchemaAwareApplyOperation to provide
    more granular operations as
       - verifyStructure - verify if correct tree node types are used
       - isApplicable - verifies if modification is applicable to other
           snapshot

  Added test suite which tests InMemoryDOMStore, performance
  of DOMDataBroker and DOM Data Broker.

Change-Id: Ia7f8659aa128e1dc1e9a8580ac46452dfe66289a
Signed-off-by: Tony Tkacik <ttkacik@cisco.com>