wip, build structure representation from visuals

src/mol-app/ui/entity/tree.tsx

src/mol-app/ui/transform/ball-and-stick.tsx

src/mol-app/ui/transform/list.tsx

src/mol-geo/representation/structure/ball-and-stick.ts

src/mol-geo/representation/structure/index.ts

src/mol-geo/representation/structure/spacefill.ts

src/mol-geo/representation/structure/utils.ts

src/mol-geo/representation/structure/visual/element-point.ts

...mol-geo/representation/structure/visual/element-sphere.ts

...presentation/structure/visual/intra-unit-link-cylinder.ts

src/mol-geo/theme/index.ts

src/mol-geo/theme/structure/size/index.ts

src/mol-geo/theme/structure/size/physical.ts

src/mol-view/stage.ts

src/mol-view/state/entity.ts

src/mol-view/state/transform.ts