Sync volume versionedobject to ORM

Sync volume versionedobject to ORM

The following patch syncs the volume object to match the
ORM.  More specifically, it adds metadata, admin_metdata,
volume_attachment, and volume_type to the volume object.
These fields are required to convert cinder internals to
use volume versionedobject.  It was originally part of
a large patch, but is broken up to make reviews more
bearable.

Change-Id: I80c1734072cb26acbe207914e812a3b169b69dfb
Partial-Implements: blueprint cinder-objects