wip, terminal gaps

src/mol-geo/primitive/pyramid.ts

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

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

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

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

...l-model/structure/model/properties/utils/atomic-ranges.ts

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

src/mol-repr/structure/visual/polymer-gap-cylinder.ts

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

...l-repr/structure/visual/util/polymer/backbone-iterator.ts

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