segmentation & refactoring

src/mol-base/collections/_spec/equiv-index.spec.ts

src/mol-base/collections/_spec/int-tuple.spec.ts

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

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

src/mol-base/collections/_spec/linked-index.spec.ts

src/mol-base/collections/_spec/ordered-set.spec.ts

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

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

src/mol-base/collections/_spec/sorted-array.spec.ts

src/mol-base/collections/impl/segmentation.ts

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

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

src/mol-base/collections/segmentation.ts

src/perf-tests/sets.ts