Support multiple models in StructureElement.Loci.toScriptExpression

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

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

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