wip, refactored visual's mark funciton

src/mol-geo/representation/structure/complex-visual.ts

src/mol-geo/representation/structure/units-visual.ts

...esentation/structure/visual/carbohydrate-link-cylinder.ts

...presentation/structure/visual/carbohydrate-symbol-mesh.ts

...ntation/structure/visual/cross-link-restraint-cylinder.ts

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

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

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

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