wip, themeing, coloring, location iterator

...presentation/structure/visual/carbohydrate-symbol-mesh.ts

...ntation/structure/visual/cross-link-restraint-cylinder.ts

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

...mol-geo/representation/structure/visual/element-sphere.ts

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

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

.../representation/structure/visual/nucleotide-block-mesh.ts

...resentation/structure/visual/polymer-backbone-cylinder.ts

...epresentation/structure/visual/polymer-direction-wedge.ts

...o/representation/structure/visual/polymer-gap-cylinder.ts

...geo/representation/structure/visual/polymer-trace-mesh.ts

src/mol-geo/representation/structure/visual/util/common.ts

...representation/structure/visual/util/location-iterator.ts

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

src/mol-geo/theme/structure/color/chain-id.ts

src/mol-geo/theme/structure/color/element-index.ts

src/mol-geo/theme/structure/color/element-symbol.ts

src/mol-geo/theme/structure/color/index.ts

src/mol-geo/theme/structure/color/instance-index.ts

src/mol-geo/util/color-data.ts