QPID-5653: Replace DurableConfigurationStore/MessageStore recoverers with visitors.

* MS/DCS impls now have stateless visitXXX methods to retrieve message/configuration data (replaces the recoverXXXX methods)
* VH implementations now uses Handlers to perform the recovery operation.
* DCS's handler (ConfiguredObjectRecordRecoveverAndUpgrader) currently implemented in terms of the old DefaultUpgradeProvider/DurableConfigurationRecoverer.
  This will be refactored by a future commit.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1584600 13f79535-47bb-0310-9956-ffa450edef68