Switch to new pattern for extending services when creating plugin tokens + plugin interfaces.

src/services/plugin.ts

@@ -1,8 +1,9 @@
 // Copyright (c) Jupyter Development Team.
 // Distributed under the terms of the Modified BSD License.
 
-import * as services
-from 'jupyter-js-services';
+import {
+  createServiceManager, IServiceManager as IBaseServiceManager
+} from 'jupyter-js-services';
 
 import {
   Token
@@ -26,7 +27,7 @@ const IServiceManager = new Token<IServiceManager>('jupyter.services.services');
  * The service manager interface.
  */
 export
-interface IServiceManager extends services.IServiceManager { };
+interface IServiceManager extends IBaseServiceManager { };
 
 
 /**
@@ -37,6 +38,6 @@ const servicesProvider: JupyterLabPlugin<IServiceManager> = {
   id: 'jupyter.services.services',
   provides: IServiceManager,
   activate: (): Promise<IServiceManager> => {
-    return services.createServiceManager() as Promise<IServiceManager>;
+    return createServiceManager() as Promise<IServiceManager>;
   }
 };