Add rpcexplorer to webapp hierarchy.

web/inc/rpcexplorer/rpc-editor.html

 <!--
   Copyright 2016 The LUCI Authors. All rights reserved.
   Use of this source code is governed under the Apache License, Version 2.0
   that can be found in the LICENSE file.
-  -->
+-->
 
 <link rel="import" href="../bower_components/polymer/polymer.html">
 
 <script src="third_party/ace/ace.js"></script>
 <script src="third_party/ace/ext-language_tools.js"></script>
 <script src="third_party/ace/mode-json.js"></script>
 
 <link rel="import" href="rpc-completer.html">
 
 <!-- The `rpc-editor` is an Ace editor for JSON with optional autocomplete -->
@@ skipping 78 matching lines @@
         this._syncing = true;
         try {
           action.call(this);
         } finally {
           this._syncing = false;
         }
       }
     });
   </script>
 </dom-module>