Improve node synchronization in ModelRenderer and a few layouts.
Enhance Item's synchronize... methods
Use Item's synchronization in SequentialLayout
Fix the synchronization for different nodes in ModelRenderer
Remove the synchronization methods of Layout - they are not used
Convert VArrayInitializer to the declarative framework
Remove the synchronization methods of GridLayout - they are not used
Use EmptyItem instead of NodeWrapper in VClass and VClassSzPublic
Use Item's synchronization method in declarative item wrappers
Enhance the synchronizeWithNodes method of GridLayout
Introduce a generic method to synchronize two collections and use it
Use the generic synchronizeCollection also in PositionLayout