Revert "Added Screen interface"

This reverts commit 90c3d18f19.

src/sdlf/Screen.hpp

@@ -1,21 +0,0 @@
-#pragma once
-
-#include "SDL.h"
-
-namespace sf
-{
-	class IScreen
-	{
-	public:
-
-	protected:
-		IScreen();
-
-		virtual void OnFocus() = 0;							// Called when the screen is being switched to
-		virtual void OnDefocus() = 0;						// Called when the screen is being switched from
-		virtual void OnUpdate(double frametime) = 0;		// Called every frame
-		virtual void OnEvent(const SDL_Event& event) = 0;	// Called after an event occurs
-	
-	private:
-	};
-}