With these changes, I'd also like to propose that we move ASNodeController
out of Beta (renaming the files without +Beta). Let me know what you think!
Because we don't support ASNodeController directly in ASCV / ASTV, it is still
important to allow flipping the ownership in certain cases (in particular, for
root CellNodeController objects that should follow the lifecycle of the
ASCellNode rather than owning the ASCellNode).
* [ASNodeController+Beta] Provide an option to allow nodes to own their controllers.
We should certainly remove this before moving ASNodeController out of Beta. However, I think
it will require at least ASCollectionNode to be able to retain its top level set of node controllers.
Without this facility built in, it's very difficult for apps supporting both UIKit and ASDK to
manually manage the controllers and keep them in sync with perfect timing.
* [ASNodeController] Fix one of the #if's.
