renamed MaterialInstance to MaterialParameters.

example/2dVector/line.cpp

@@ -35,7 +35,7 @@ private:
 
     Camera cam;
 
-    MaterialInstance *  material_instance   =nullptr;
+    MaterialParameters *  material_instance   =nullptr;
     RenderableInstance *render_instance     =nullptr;
     GPUBuffer *         ubo_camera_info    =nullptr;
     GPUBuffer *         ubo_color_material  =nullptr;