Updated ElementSet API

src/apps/render-test/state.ts

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

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

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

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

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

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

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

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

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

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

src/perf-tests/structure.ts