per-unit dssp as structure property

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

src/mol-model-props/computed/secondary-structure.ts

src/mol-model-props/computed/secondary-structure/dssp.ts

...l-props/computed/secondary-structure/dssp/trace-lookup.ts

...ol-model/structure/model/properties/seconday-structure.ts

src/mol-repr/structure/visual/util/polymer/trace-iterator.ts

src/mol-theme/color/secondary-structure.ts