Ships implement ISteerable interface.
-the ships speed and direction can be controlled by the player.
-There is only one ship in the game at any one time (Singleton pattern).
-Initial location should be in the center of the world (512, 384).
-Initial speed of zero and a heading of north 90 degrees.
-Ships have an attribute called missile count an integer representing the number of missiles the ship has available to be fired. Max number of starting missiles is 12.
-Each time a ship fires a missile its missile count is decremented by one; When missile count reaches zero it can no longer fire any missiles.
-ship that fly to a space station automatically have their missile count reloaded to the original maximum number.