closed #5482: fix issue: Node::setPhysicsBody() doesn't work after node added to other node.
closed #5482: add a test case for bug 5482.
Merge pull request #6963 from andyque/refactorLayout

refactor Layout, remove sortChildren and unify doLayout
Merge pull request #6969 from boyu0/bug5482_setPhysicsBody

closed #5482: Node::setPhysicsBody() doesn't work after node added to another node.