Update copyright notice from Swarming to LUCI; add AUTHORS and CONTRIBUTORS.

appengine/gce-backend/state_machine.py

-# Copyright 2015 The Swarming Authors. All rights reserved.
+# Copyright 2015 The LUCI Authors. All rights reserved.
 # Use of this source code is governed by the Apache v2.0 license that can be
 # found in the LICENSE file.
 
 """GCE Backend instance state machine."""
 
 import collections
 
 import models
 
 
@@ skipping 56 matching lines @@
           'pubsub_subscription_project': instance.pubsub_subscription_project,
           'pubsub_topic': instance.pubsub_topic,
           'pubsub_topic_project': instance.pubsub_topic_project,
       },
       'update-instance-metadata',
       '/internal/queues/update-instance-metadata',
       models.InstanceStates.UPDATING_METADATA,
       models.InstanceStates.PENDING_METADATA_UPDATE,
   ),
 }