add basic psf reader

src/mol-io/reader/_spec/psf.spec.ts

src/mol-io/reader/common/text/tokenizer.ts

src/mol-io/reader/psf/parser.ts

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

src/mol-plugin/state/actions/data-format.ts

src/mol-plugin/state/actions/structure.ts

src/mol-plugin/state/objects.ts

src/mol-plugin/state/transforms/data.ts