* Refactored ManualLoader out of the Engine and into the game
* Moved initialization code into ManualLoader and out of Main
* Vector2D is now an inmutable class
+ New empty constructor for PositionComponent with position defaulting
to 0,0
+ Created WeaponComponent to hold bulletSize, bulletDirection and
bulletSpeed (by now). Should be called GunComponent, though.
+ Created EntityFactory
+ Created empty TimerSystem
+ Inherited GameComponent from Component to hold the names of game-based
(as opposed to engine-based) components.
+ Created bullet factory.
+ Created useless enemy factory.