Removed GUIView

- We're not currently using it, and we might end up restructuring how our GUI stuff works anyway. If we need to view it as an example, it's included in our most recent Cooper prototypes.
Refactored PathfinderAI

- Added MoveAlongPath(). It feels better to handle all pathfinding related functionality in the PathfinderAI class than in the EnemyCharacterController. Also allows us to lock down some variables that probably have no business being public.
Removed view-related classes

- We're not currently using any view/animation-related stuff yet, so let's get rid of the clutter. When we're ready to implement animations, there are examples of using the view classes in the Cooper prototypes repo.
Commented and cleaned up CollisionHandler classes.
Refactored state-related classes.

- Any movement/velocity related variables, properties, or methods should be contained within the MoveableObject class.
- Make Die() an abstract method to be overridden by the subclass.
Added ReticleController.MoveBy()
Added additional method signature for MoveableObject.Move().

- Removed MoveableObject.AddVelocity(). Currently unused.
Refactored Controller-related classes.