Editor plugin: Edit element via double click

Pdf4QtEditorPlugins/EditorPlugin/editorplugin.h

@@ -57,6 +57,7 @@ private:
     void onWidgetSelectionChanged();
     void onToolActivityChanged();
     void onSceneEditElement(const std::set<pdf::PDFInteger>& elements);
+    void onSceneEditSingleElement(pdf::PDFInteger elementId);
 
     void onPenChanged(const QPen& pen);
     void onBrushChanged(const QBrush& brush);