refactored representation-to-renderItem pipeline

src/mol-geo/representation/index.ts

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

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

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

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

src/mol-geo/representation/volume/surface.ts

src/mol-geo/shape/mesh.ts

src/mol-geo/shape/vertex-map.ts

src/mol-geo/util/color-data.ts

src/mol-geo/util/marching-cubes/algorithm.ts

src/mol-geo/util/mesh-data.ts

src/mol-geo/util/size-data.ts

src/mol-gl/TODO

src/mol-gl/_spec/renderer.spec.ts

src/mol-gl/render-object.ts

src/mol-gl/renderable.ts

src/mol-gl/renderable/mesh.ts

src/mol-gl/renderable/point.ts

src/mol-gl/renderable/schema.ts

src/mol-gl/renderable/util.ts