Removed deadline, version, extra & host_aggregate

As we are about to version the Watcher objects, we need to make sure
that upcoming model/object modifications are additive in order to
avoid having to bump the major version of the API. Therefore,
this changeset removes 4 unused DB fields that were exposed in their
associated Watcher objects (i.e. AuditTemplate and Audit).

Change-Id: Ifb0783f21cd66db16b31e3c8e376fc9d6c07dea3
Partially-Implements: blueprint watcher-versioned-objects

watcher/db/api.py

@@ -275,7 +275,6 @@ class BaseConnection(object):
                          'name': 'example',
                          'description': 'free text description'
                          'goal': 'DUMMY'
-                         'extra': {'automatic': True}
                         }
         :returns: An audit template.
         :raises: :py:class:`~.AuditTemplateAlreadyExists`
@@ -375,7 +374,6 @@ class BaseConnection(object):
                         {
                          'uuid': utils.generate_uuid(),
                          'type': 'ONESHOT',
-                         'deadline': None
                         }
         :returns: An audit.
         :raises: :py:class:`~.AuditAlreadyExists`