Moved Model::EnableDraw to SceneNode::EnableDrawing

Same goes for Model::IsDrawEnabled() => SceneNode::IsDrawingEnabled()
Is Drawable is now a pure virtual method from SceneNode


Former-commit-id: 217c6a21a98206ee0b283aaa216d419696a70faf

include/Nazara/Graphics/SceneRoot.hpp

@@ -20,6 +20,8 @@ class NAZARA_API NzSceneRoot : public NzSceneNode
 		const NzBoundingVolumef& GetBoundingVolume() const override;
 		nzSceneNodeType GetSceneNodeType() const override;
 
+		bool IsDrawable() const;
+
 	private:
 		NzSceneRoot(NzScene* scene);
 		virtual ~NzSceneRoot();