basic structure selection model, fixed bug in OrderedSet

src/mol-canvas3d/canvas3d.ts

src/mol-canvas3d/helper/interaction-events.ts

src/mol-data/int/_spec/ordered-set.spec.ts

src/mol-data/int/impl/ordered-set.ts

src/mol-geo/geometry/marker-data.ts

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

src/mol-plugin/behavior/dynamic/camera.ts

src/mol-plugin/behavior/dynamic/representation.ts

src/mol-plugin/behavior/static/state.ts

src/mol-plugin/command.ts

src/mol-plugin/context.ts

src/mol-plugin/ui/viewport.tsx

src/mol-plugin/util/loci-label-manager.ts

src/mol-plugin/util/structure-element-selection.ts

src/mol-repr/representation.ts

src/mol-util/input/input-observer.ts