Merge pull request #114 from redding/jcr-server-config-data

Add `Server::ConfigData`, make `HostData` compatible
Rename `Worker` to `WorkerOld`

This is to free-up the name `Sanford::Worker` for new logic that
goes with the new `Sanford::Server`. This keeps the old sanford
logic still working while we rework its logic in a new stack.