Add rug-ctl command to reload config

Add a command to have the worker reload the configuration file(s). This
will be useful when we automatically deploy new router images, since
we can change the running RUG without restarting it and losing any work
that is happening at the time.

Change-Id: I08628b1292e0e5a26dc3382c790dd41a806716bb
Merge pull request #116 from dhellmann/update-config-command

Add rug-ctl command to reload config