SceneDesc: Make code a bit more readable. Add some EntityDest IsParentFor(). Add list typedefs for scene desc structs.
EntityReference: Early out for IsEmpty(). Update deprecated function calls to Scene.
Scene: Optimizations for loading large scenes with heavy parenting. Main focus was on CreateContentFromSceneDest(). It will now order the EntityDescs so that parents code first. Also fixed the code duplication of updating Placeable::parentRef from old to new ids, moved as a utility function (used in all xml/binary/desc imports). Other minor tweaks and fixes like not using Qt foreach for non pointers (even if you use const & it will make a copy of the container under the hood).
Placeable: Performance optimizations. Implement tracking child Placeables by weak ptrs (was a todo note in Children()). Disconnect comp added from parent when no longer needed and other minor tweaks. For large scenes Children() was impossibly slow, it iterated the whole scene and for each Entity called EntityReference::Lookup() that in worst case iterated the scene again (name based parenting). After my recent bugfix to Show() Children() was called in it, and Show() was in turn called from AttributesChanged(). This made big imports so slow that they would not complete before server already disconnects the client (before even getting anything to the network).
Cleanup qdebug from shadow stuff and remove ugly formatting.