onCollision version with parameters that are "backward compatible" with ...

There is an open question as to how to best handle onCollision in behaviors.

Say two objects A and B collide.  T2D has the option to handle onCollision with either the Scene or with the objects themselves.  If handling with the scene, you have

    myScene::onCollision(%this, %objectA, %objectB, %details)

where you get both objects, of course.  If handling with the objects themselves, you have

    myObject::onCollision(%this, %objectB, %details)`

The called object is objectA or `%this`.  The question is if handling with behaviors, what do you prefer?  Original it was

    1) myBehavior::onCollision(%this, %objectB, %details)

That is, to get objectA,  you use `%this.owner`.  A recent experiment changed it to

    2) myBehavior::onCollision(%this, %parentObjectA, %objectB, %details)

That is, you also get the owner (objectA) directly as `%parentObjectA`.

Opinions?  Don't cares?

The current pull request would switch it back to 1) above.  Canceling this pull request would keep it at the new 2).