Reconnect outlet to constraints

fixes #6

During loading, we replace the layout constraints to the “container view” with new constraints to the actual view.  We must also update any outlets to those constraints.

I’m not entirely satisfied with my solution to list the outlets of the view (by overloading `setValue:forKey:`). @Codewaves’s solution (see #6) involved listing the object properties via `objc_` runtime methods, which is _not that great_ and doesn’t work with ivar outlets.