wip, nominal Element and Element.Index

src/mol-data/int/ordered-set.ts

src/mol-data/int/sorted-array.ts

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

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

src/mol-model/structure/query/modifiers.ts

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

src/mol-model/structure/query/utils/builders.ts

src/mol-model/structure/query/utils/structure.ts

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

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

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

src/mol-model/structure/structure/util/lookup3d.ts

src/mol-model/structure/structure/util/subset-builder.ts

src/mol-view/label.ts

src/perf-tests/lookup3d.ts