SSH connection extended by an optional (chain of) jumphost.

Publish over SSH supports jumphosts.
Jumphosts can be entered separated by space (and comma and semiconlon) and the SSH-connection to target is setup via the jumphosts one by one.
- Unittests added to check the analysis of entered jumphosts
- Tests added to check thet createClient creates (and disconnects) additional sessions
Ideas for improvement: Different user, ports, keys for jumphosts