Fixed xterm.py (and cleanup) to clean up screen sessions.
Cleaned up sshd.py (though interface is still in flux.)
Added 1024-node network example (treenet1024.py).
Added example showing multiple tests on a single network (multitest.py).
Renamed examples to make them easier to type!

Other minor cleanup.

Modified cleanup to use dpctl to remove kernel datapaths.

Node -> { Host, Switch, Controller }
Network -> { TreeNet, GridNet -> LinearNet }

Modified cleanup to clean up kernel datapaths.