SLA support points improvements

- semi-intelligent algorithm to place support points
- enhanced ImGui dialog with editing/non-editing mode
- support points can have different head diameter (only implemented in GUI so far)
- autogenerated points supporting emerging islands are annotated and the info is kept

src/slic3r/GUI/GLCanvas3D.hpp

@@ -779,11 +779,7 @@ private:
 
         void set_flattening_data(const ModelObject* model_object);
 
-#if ENABLE_SLA_SUPPORT_GIZMO_MOD
         void set_sla_support_data(ModelObject* model_object, const GLCanvas3D::Selection& selection);
-#else
-        void set_model_object_ptr(ModelObject* model_object);
-#endif // ENABLE_SLA_SUPPORT_GIZMO_MOD
         void clicked_on_object(const Vec2d& mouse_position);
         void delete_current_grabber(bool delete_all = false);