Surface: ViewProviderExtend for Surface::Extend object

This is created by the Surface_ExtendFace command.

src/Mod/Surface/Gui/AppSurfaceGui.cpp

@@ -37,6 +37,7 @@
 #include "TaskGeomFillSurface.h"
 #include "TaskFilling.h"
 #include "TaskSections.h"
+#include "ViewProviderExtend.h"
 
 // use a different name to CreateCommand()
 void CreateSurfaceCommands(void);
@@ -81,8 +82,8 @@ PyMOD_INIT_FUNC(SurfaceGui)
     SurfaceGui::ViewProviderGeomFillSurface ::init();
     SurfaceGui::ViewProviderFilling         ::init();
     SurfaceGui::ViewProviderSections        ::init();
-    
-//    SurfaceGui::ViewProviderCut::init();
+    SurfaceGui::ViewProviderExtend::init();
+    // SurfaceGui::ViewProviderCut::init();
 
     PyObject* mod = SurfaceGui::initModule();
     Base::Console().Log("Loading GUI of Surface module... done\n");