wip, strongly typed indexes in Model

src/mol-data/db/column.ts

src/mol-model/structure/model.ts

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

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

src/mol-model/structure/model/formats/mmcif/bonds/comp.ts

...-model/structure/model/formats/mmcif/bonds/struct_conn.ts

...ucture/model/formats/mmcif/pair-restraints/cross-links.ts

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

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

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

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