Allow an easy deployment on k8s infrastructure (gracedb-test01.igwn.org/minikube)

Merge request connected to issue: #293

• Allow for hostname not in the domain ligo.org (0002_update_site.py)
• Add a variable in DOCKER file to set IGWN_ALERT_AUTH to false (not using authentication)
• Allow to use an igwn-alert configuration that does not require authentication (base.py)

Related merge request (not needed to work on the official deployment):

• Allow overseer to connect to an hop server without authentication computing/igwn-alert/overseer!3 (diffs)