* Port VectorData to Instances<VectorData>
* Port ImageFrame<P> and TextureFrame to Instances<ImageFrame<P>> and Instances<TextureFrame>
* Avoid mutation with the TransformMut trait
* Port GraphicGroup to Instances<GraphicGroup>
* It compiles!
* Organize debugging
* Document upgrading
* Fix Brush node
* Restore TransformMut in lieu of TransformSet trait
* Fix tests
* Final code review