Fixed a bug that caused the simulation to never move the ball.
Last bit of the refactoring from two commits ago.
Changed how the class behaves before positions and orientations have been set for the first time - it now returns null vectors instead of (1,1) vectors.
Like the last commit but for orientation.
Changed MobileObject not to allow zero time difference between two frames in history, enforced in the set methods.
Added simple test file for the world model.
Updated world model to allow conversion from pixels to some other unit (cm).
TestWorld now resets the world before each new test.