WIP: networker skeleton

worker: networker skeleton

This RP is a skeleton for the future networker based on StringsWorker

Continue of work from: https://github.com/juju/juju/pull/86
I don't know the easy way to search in slice. What is wrong with my format?
The alternative is to use readyInterfaces = map[string]bool{"eth0":true, "eth1":true}