chore(logging): Use the builtin log package

Several log lines had to change, as they were simply logging
duplicate timestamps.
refactor(registry): Move Address code to Machine

The logic for inspecting and parsing a system's interfaces into Addr objects
now lives in Machine.GetAddresses
chore(agent): Add some simple documentation of Agent
refactor(*): Break apart files into packages
refactor(agent): Remove remaining etcd access from Agent
refactor(agent): Expand log statements