QPID-5685: Store configuration version as an attribute of virtualhost within configuration store rather than within separate database/table

* ConfiguredObjectRecordHandler begin/end methods no longer take/return config version
* DefaultUpgraderProvider uses the virtualhost record for the config version only and uses this to trigger
  the correct upgrade.  Note this record is *not* recovered (yet).
* BDB/SQL Upgraders migrate the config version from database/table to be the modelVersion attribute of a virtualhost entry.
* BDB Upgrader tests (7 to 8).

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1587165 13f79535-47bb-0310-9956-ffa450edef68