modified the containsPoint method so that a line consisting only of one
point does not cause a bug for other lines with the same y coordinate
anymore
restructured MyObjectCentralisation and added IllegalStateException if
no object to centralise on can be found
the Picker now goes down in case no blue colour could be detected, moves
5cm back and goes up again - this prevents trouble if the ball was
picked but is not really inside the claw (the trouble will be recognised
when the ball should be dropped)