Fixed a bug where balls collided with themselves

The recent changes in the updateBalls method changed a double for loops
over all balls to a single for loop over all balls with a call to
inBall. However this did not check if the collided with target was the
same ball resulting in a colission with self and an inf/NaN force since
the distance between them is zero.
Fixed tennisball bugs

Fixed bugs with tennisbal being too big and not drawn at the correct
position. Colissions with tennisballs remains.
Fixed the final collision bugs

Caused by the collision checking method overestimated the collision
radius which caused failure in the time estimation algorthm. Reasonably
i should make that method safer so that it throws an exception or
something when a faulty case is given.