Split ship movement in several systems:
- ShipControl to handle events (mostly state transitions) of single ships
- ShipsMovement to handle the basic movement of the ship (this will update the position of the ship)
- ShipsMoving to handle ships that are in the 'moving' state
- ShipsOrbiting to handle ships that are in the 'orbiting' state

Plantes and asteroids are now recognized as obstacles for ships.