added assembly property to SymmetryOperator; improved AssemblySymmetry

src/mol-math/geometry/spacegroup/construction.ts

src/mol-math/geometry/symmetry-operator.ts

src/mol-model-props/rcsb/assembly-symmetry.ts

...odel-props/rcsb/representations/assembly-symmetry-axes.ts

src/mol-model-props/rcsb/themes/assembly-symmetry-cluster.ts

src/mol-model-props/rcsb/util.ts

src/mol-model/structure/model/formats/mmcif/assembly.ts

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

src/mol-model/structure/query/queries/internal.ts

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

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

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

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

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

...l-model/structure/structure/util/unique-subset-builder.ts