add a non-standard sequence for stream-opt -> opt-stream

what is the usecase of this thing? we have a lot of `Optional<Stream<...>>` in Bio4j. As I understand, you want to imitate `NonEmptyList` with `Optional<Stream<...>>` when the optional is present, but I don't see the point, `Optional` is always an obstacle when working with it, it doesn't give you anything.