Allow a way to SSH in to box

[MarkBennett]

This would be useful when running and testing commands from the individual plow recipes.

[mm53bar]

Does this make sense if you have multiple boxes? I would think that it could be made available but only if the SERVERS array has a length of 1.

[jbabe]

Even a list of servers would be good enough - what about a bin/plow servers

[jbabe]

bin/pave list does this already - good enough for now?