[squeakland] Collision detection, only one object detects the collision

[Karl Ramberg]

Hi,
i've been playing with the overlaps and overlapsAny and I think I have 
fixed a bug,
but I'm not completely satisfied because I think the sibling issue 
confuse and complicates here.
Current implementation detects non Players that are of the same class or 
Players that are siblings.

I think we could have this test divided into two tests:
overlapsAny (all player costume class overlaps returns true)
and
overlapsAnySibling (only sibling overlaps return true)

This to  make the behavior explicit. It is confusing when the test fails 
because the Player is a copy and not a sibling.

There are also other issues here that are confusing to beginners:
To a kid a sketch of a dog is very different to a sketch of a tree.
To return true on overlapsAny dog when overlapping a tree is confusing.

What are your thoughts on this ?

Karl