refs #735, allow to reset highlighting

(some leftovers of DB object highlighting also deleted)

src/blackgui/models/listmodelbase.h

@@ -111,6 +111,9 @@ namespace BlackGui
             //! Hovered role
             void setHoveredRow(int row);
 
+            //! Remove all highlighting
+            virtual void clearHighlighting();
+
             //! Drop actions
             void setDropActions(Qt::DropActions dropActions) { this->m_dropActions = dropActions; }