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

appengine/auth_service/proto/config.proto

-// 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.
 
 // Configuration schema for configs fetched via a config service.
 
 package auth_service;
 
 
 // Configuration of cron job that imports groups from external sources.
 message GroupImporterConfig {
@@ skipping 109 matching lines @@
     // allowed (default). Format of the entries:
     //     user:abc@example.com - identity
     //     user:*@example.com - identity glob
     //     group:group-name - group
     repeated string allowed_to_impersonate = 4;
   }
 
   // Rules are evaluated sequentially until the first hit.
   repeated Rule rules = 1;
 }