#20 IP address change needs restart

[Joseph Hopfield]

Notebooks (especially) often move from network to
network (wireless & wired) and change ip addresses
without rebooting.

When the agent's ip address changes, the agent must
be restarted. The agent should re-check the local ip
address on error & periodically.

Somehow host.Host.run() should call startRMIServer if
there's been an error talking to the existing server, or
could just check on every loop (5 secs or whatever).
Not expensive (I think).