wip, computed secondary structure prop

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

...-model-props/computed/secondary-structure/dssp.validation

...model-props/computed/secondary-structure/zhang-skolnik.ts

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

...ior/dynamic/custom-props/pdbe/structure-quality-report.ts

src/mol-repr/structure/complex-visual.ts

src/mol-repr/structure/units-visual.ts

src/mol-repr/structure/visual/polymer-direction-wedge.ts

src/mol-repr/structure/visual/polymer-trace-mesh.ts

src/mol-repr/structure/visual/polymer-tube-mesh.ts

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

src/mol-repr/util.ts

src/mol-theme/color.ts

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

src/tests/browser/render-structure.ts