Graphics/Shadows: Add directional shadow mapping (WIP)

It still needs some debug


Former-commit-id: 029872debc1a784712a33802ddd70a2b61e55623

include/Nazara/Graphics/AbstractRenderQueue.hpp

@@ -59,7 +59,9 @@ class NAZARA_GRAPHICS_API NzAbstractRenderQueue
 		struct DirectionalLight
 		{
 			NzColor color;
+			NzMatrix4f transformMatrix;
 			NzVector3f direction;
+			NzTexture* shadowMap;
 			float ambientFactor;
 			float diffuseFactor;
 		};