Server + Client reorganization

Client:
- Split the Graphics class into two new classes that derive from the
abstract class Renderer: GameRenderer and MenuRenderer.
- Added a GameLoop class that will perform any client-side logic +
invoke the Render Method.

Server:
- Added a 2D Vector Integer Class.
- Added a Map class.
- Added a MapManager class.
- Added a NPC class which derives from the interface IEntity
- Added a new function which calculates damage.
- Added a OnDeath method for Entities.