Animate cell deselection only when navigating back to that table view

All the standard iOS navigation table views keep the cell selected until navigating back, animating it back to deselected as the table comes into view. This gives the user context to where they came from.

This pull request adds that functionality into the core MT.D elements, and adds an ActiveController overload that lets external code also opt in to this behaviour. I didn't delete the original method to maintain backwards compatibility, but it should be considered as this animation is part of the Apple HIG.