API to DB Object Refactoring

This change incorporates object abstraction for DB objects as used
in the Ironic and Nova openstack projects.  As part of the
refactoring, a new module "cue/objects" has been created.  This
module provides generalized access to DB objects.  As part of this
patch, The API has also been updated to access DB objects through
the "cue/objects" module.

* updating affected tests.

Change-Id: Ia3fee13c713ea6a887875004933436e64dbd121d