corected testmethod for Trusters constructor
corected testmethod for Trusters getRotationAcceleration method
corected testmethod for Trusters getAcceleration method
added method getSetOfDrawables in IDrawable
changed method in IDrawable to return a collection that extends IDrawable and calld that method in Gameworld when making list of DrawableData
Implemented getColectionDrawables
Implemented getColectionDrawables in WeaponPickup
Implemented getColectionDrawables in HealthPickup
Implemented getColectionDrawables in Missile
Implemented getColectionDrawables in Bullet
Implemented getColectionDrawables in Spaceship
removed unneded methods in Spasceship.(get-methods for thrusters in Spaceship)
fixed mergeconflict