* Simplify applying layout transition in preparation for bigger layout transition API work
* Change from apply to complete in if layout transitions are involved and _applyLayout: to _setCalculatedLayout: for layout
* Change to applySubnodeInsertions and applySubnodeRemovals
* Change from completeTransition to commitTransition and flip logic around when to trampoline to the main thread for implicit hierarchy management
* More internal API improvements
* Fix merge conflicts
* Rename _layout to _calculatedLayout
Currently measurement always needs to happen on the main thread if implicit hierarchy management is enabled as adding and removing from nodes needs to happen on the main thread. We now will trampoline to the main thread to do the insertion and deletion of nodes.
This also resolves the issue that can occur if a node is already loaded deep in the layout hierarchy in the layout that the node is transforming to. Before insertion or deletion is happening we need to crawl the layout hierarchy to check that though.
