This extension point allow other plug-ins to act on metadata information extracted by Quantum. For each registered extension, Quantum will add a menu entry in the context menu of the Bookmarks View. The label of the metadataActor. Will be used to appear in the context menu. The class acting on the metadata. Will be supplied by the external plug-in, not by Quantum. 2.3 [Enter extension point usage example here.] [Enter API information here.] [Enter information about supplied implementation of this extension point.]