#19 Shutdown or restart model

[Michael Nash]

Create a model that can (with appropriate security, of
course!) shut down a specific Keel server in a cluster.
If the script that starts the Keel server is in a loop, it
will then re-start that server with new config and libs.
This provides a way to update each server in a cluster
one at a time, while leaving the other servers running
so there is zero downtime for users.