Recursive Download

[f0o]

Is your feature request related to a problem? Please describe. Title states it; A way to recursively download objects when the object-key ends in a slash.

Describe the solution you'd like Parity with gcloud's gsutil in this regard (gsutil cp -r)

Describe alternatives you've considered repeated ls and issuing xargs to download all files; however it's tedious and ugly.

Additional context ./.