This class represent a bullet
Inheritance: CDrawableComponent
 /// <summary>
 /// Add a new bullet at the specified position, rotation and direction
 /// </summary>
 /// <param name="position">initial position of the new bullet</param>
 /// <param name="rotation">rotation of the new bullet</param>
 /// <param name="direction">Direction in which the bullet will move</param>
 public void AddBullet(Vector3 position,Vector3 rotation, Vector3 direction)
 {
     Bullet bullet = new Bullet(myGame, Game.Content.Load<Model>("projectile"),
         new BulletUnit(myGame, position, rotation, Constants.BULLET_SCALE, direction));
     bullets.Add(bullet);
 }