container: Expose create and destroy ChildMeta methods
It is conceivable that Container implementations might add children outside of the Container::add() implementation - e.g. for packing at a specific index. Since the addition (and removal) might happen outside the common path we need to expose all the API that is implicitly called by ClutterContainer when adding and removing a child - namely the ChildMeta creation and destruction.
Showing with 38 additions and 12 deletions