added label propertiy to representation interface

src/mol-geo/representation/index.ts

src/mol-geo/representation/shape/index.ts

...ol-geo/representation/structure/complex-representation.ts

...l-geo/representation/structure/representation/backbone.ts

...representation/structure/representation/ball-and-stick.ts

...o/representation/structure/representation/carbohydrate.ts

...ol-geo/representation/structure/representation/cartoon.ts

...esentation/structure/representation/distance-restraint.ts

src/mol-geo/representation/structure/representation/point.ts

...-geo/representation/structure/representation/spacefill.ts

src/mol-geo/representation/structure/visual/element-point.ts

...presentation/structure/visual/inter-unit-link-cylinder.ts

...presentation/structure/visual/intra-unit-link-cylinder.ts

src/mol-geo/representation/util.ts

src/mol-geo/representation/volume/index.ts