TransitionManager Overhaul

This release overhauls TransitionManager and moves responsibility for managing a screen's "Out" transition (the transition that gets used when leaving a screen) from the App (which was silly) to the ScreenView itself.

This creates a much more intuitive workflow, and makes it a lot easier for a Screen to set its own transition, even set a different transition depending on what user interactions caused the Screen to exit.

Now, use ScreenView.TransitionOut setter to set any subclass of TransitionBase (including TransitionBase, if you want a straight cut) prior to calling ScreenRouter.setScreen() and you'll get the expected transition.