Refresh of TreeViewer is slow

The refresh event for the components tree viewer always performs a refresh of the entire component structure, even if only a sub-component was modified. We should pass the affected model as additional parameter to the `refreshed` method so that we can call `refresh()` on that, rather than the root.

https://github.com/eclipse-windowbuilder/windowbuilder/blob/56b01bd954bbc675a797ed9d9e434fddb7d8cef8/org.eclipse.wb.core/src/org/eclipse/wb/core/gefTree/part/ObjectEditPart.java#L90-L104