Littles fixes

-Light Manager: I prefer iterators
-OpenGL: The UV problem is solved, but you forget to change the cubemaps
-Texture: GetSize() could return a int instead a NzVector2ui
-Algorithm: Simplification
-Utility: Couldn't compile

Former-commit-id: db890711b451d03427871fb997549a1b13c7d80a

src/Nazara/Renderer/Texture.cpp

@@ -468,7 +468,7 @@ NzVector2ui NzTexture::GetSize() const
 	if (!m_impl)
 	{
 		NazaraError("Texture must be valid");
-		return 0;
+		return NzVector2ui(0, 0);
 	}
 	#endif