more refactoring

src/mol-data/sequence/TODO

src/mol-data/structure.ts

src/mol-data/structure/_spec/atom-set.spec.ts

src/mol-data/structure/model.ts

src/mol-data/structure/model/builders/mmcif.ts

src/mol-data/structure/model/constants.ts

src/mol-data/structure/model/data-format.ts

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

src/mol-data/structure/model/properties/computed.ts

src/mol-data/structure/model/properties/conformation.ts

src/mol-data/structure/model/properties/format-specific.ts

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

src/mol-data/structure/model/properties/transforms.ts

src/mol-data/structure/model/utils/hierarchy-keys.ts

src/mol-data/structure/query.ts

src/mol-data/structure/query/generators.ts

src/mol-data/structure/query/properties.ts

src/mol-data/structure/query/query.ts

src/mol-data/structure/query/selection.ts

src/mol-data/structure/structure.ts