add key to symmetry operator

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

src/mol-model-formats/structure/property/bonds/index-pair.ts

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

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

...mol-model/structure/structure/unit/bonds/inter-compute.ts

...mol-model/structure/structure/unit/bonds/intra-compute.ts

src/mol-script/language/symbol-table/structure-query.ts

src/mol-script/runtime/query/table.ts

src/mol-script/script/mol-script/symbols.ts