Add the ability to clone a widget

src/docmanager/index.ts

@@ -615,6 +615,17 @@ class DocumentManager implements IDisposable {
     return this._contextManager.getPath(id);
   }
 
+  /**
+   * Clone a widget.
+   */
+  clone(widget: Widget): Widget {
+    let parent = new Widget();
+    let id = Private.contextProperty.get(widget);
+    let name = Private.contextProperty.get(id);
+    this._createWidget(id, name, parent);
+    return parent;
+  }
+
   /**
    * Filter messages on the widget.
    */