focusIn and focusOut events for TextFlow

Focus events for the TextFlow go to the container (Sprite) that holds the actual TextLine display objects. The TextFlow has a property called flowComposer, and a flowComposer may have one or more ContainerController. Each of these ContainerControllers has a container which gets focus events. The ContainerController's focusInHandler will be called when the container gets focusIn events, and the focusOutHandler is called when it gets focusOut events. By default, all the controllers will forward the focus events to the interactionManager (ISelectionManager) if the TextFlow has one.  You can override this behavior if you like. The API docs have an example on how to do this.

- robin