Basic IHM support

src/apps/structure-info/index.ts

src/mol-data/db/table.ts

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

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

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

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

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

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

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

src/perf-tests/structure.ts