InteractionManager hit test now checks bottom-to-top

See #625

*Note:* This may break some previous applications that relied on the (incorrect) order of events.

For example, if you have a large semi-transparent sprite/hitArea that overlaps some UI behind it, the front-most sprite/hitArea will receive the input event. This is why event propagation is important for more robust input handling. For that I would propose a refactor of InteractionManager: cleaning up duplicate code, using event listeners instead of a single listener function, etc.