Move bus deployments to knative-eventing

Buses can create dispatcher and provision deployments. Previously, these
deployments were created in the same namespace as the Bus resource,
which required RBAC rules to be configured to enable the deployments to
read and update Bus, Channel and Subscription resources.

By moving these deployments into the knative-eventing system namespace,
we can use a pre-determined service account and RBAC configuration.
Since the bus-controller no longer needs to create service accounts and
role bindings, the controller can run with reduced privillage (follow
 knative#207 for that change).

Fixes knative#349

config/200-serviceaccount.yaml

@@ -21,5 +21,5 @@ metadata:
 apiVersion: v1
 kind: ServiceAccount
 metadata:
-  name: clusterbus-controller
+  name: bus-operator
   namespace: knative-eventing

config/201-clusterrolebinding.yaml

@@ -28,10 +28,10 @@ roleRef:
 apiVersion: rbac.authorization.k8s.io/v1beta1
 kind: ClusterRoleBinding
 metadata:
-  name: clusterbus-controller-manage
+  name: bus-operator-manage
 subjects:
   - kind: ServiceAccount
-    name: clusterbus-controller
+    name: bus-operator
     namespace: knative-eventing
 roleRef:
   kind: ClusterRole