[feature add] Add network support to recurse copy via network

[gaetanquentin]

trafficstars

This script works fine.

But it would be better if it could send subvols like it does via network.

tools like btrbk do it well. and data is compress via bzip or pbip2. It would be very powerfull to transfer on disk to remote one.

[mwilck]

Sounds similar to #15. I currently don't plan to implement this. If someone wants to work on it, be my guest.