wip, units visuals refactoring

src/mol-geo/geometry/geometry.ts

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

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

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

...representation/structure/visual/gaussian-density-point.ts

...epresentation/structure/visual/gaussian-density-volume.ts

.../representation/structure/visual/gaussian-surface-mesh.ts

...esentation/structure/visual/gaussian-surface-wireframe.ts

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

.../representation/structure/visual/nucleotide-block-mesh.ts

...resentation/structure/visual/polymer-backbone-cylinder.ts

...epresentation/structure/visual/polymer-direction-wedge.ts

...o/representation/structure/visual/polymer-gap-cylinder.ts

...geo/representation/structure/visual/polymer-trace-mesh.ts