Renamed Atom* to Element*

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

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

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

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

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

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

src/mol-model/structure/structure.ts

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

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

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

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

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

...mol-model/structure/structure/element/impl/set-builder.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/unit.ts

src/perf-tests/sets.ts

src/perf-tests/structure.ts