add eachLocation to representation/visual interface

CHANGELOG.md

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

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

src/mol-repr/representation.ts

src/mol-repr/shape/representation.ts

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

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

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

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

src/mol-repr/util.ts

src/mol-repr/visual.ts

src/mol-repr/volume/representation.ts