selection and various tweaks

src/mol-base/collections/_spec/iterators.spec.ts

src/mol-base/collections/equivalence-classes.ts

src/mol-base/collections/hash-set.ts

src/mol-base/collections/iterator.ts

src/mol-base/computation.ts

src/mol-data/query/generators.ts

src/mol-data/query/selection.ts

src/mol-data/structure.ts

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

src/mol-data/structure/atom-set/base.ts

src/mol-data/structure/atom-set/builder.ts

src/mol-data/structure/base.ts

src/mol-io/utils/msgpack/encode.ts