improved gro format reading

src/mol-model-formats/structure/common/component.ts

src/mol-model-formats/structure/common/util.ts

src/mol-model-formats/structure/gro.ts

src/mol-model-formats/structure/pdb/entity.ts

src/mol-model/structure/model/properties/atomic/hierarchy.ts

...-model/structure/model/properties/utils/atomic-derived.ts

src/mol-model/structure/model/types.ts

src/mol-util/set.ts