Use the 'sync' worker still due to issues with handling file
uploads when gunicorn uses at least 6 but possibly more than 2
workers.

These settings were previously handled in settings/container/production.py,
but we want to do some testing and I don't see any issues with having
them in the base container settings (settings/container/base.py).

Upgrade gunicorn to 19.9.0 and switch to an asynchronous
worker class

Instead of looping over EmailMessage.send() calls, we now get the
email backend and send a list of messages. Note that the backend
sends the messages individually still but this cuts out some of the
overhead.

Not feasible to use multiple DBs for read or write operations at
present. We're going to have to revisit this at some point. We leave
most of the code in place but commented out.

Small fixes to the main "index" view for alerts. Move the
manage_password page for LV-EM observers to the ligoauth app and
show a link to it from the navbar to those users.

Separate phone and email contacts, add verification of contact
information, improve views and forms.

Since the web view makes a few API requests to load log messages and
other content, we have to allow more requests. Also, it sounds like
users at a university might all appear to be on the same IP address,
so we want to try to account for that.

Not working as expected, so we are going to have to revisit this
feature in the near future.

These environment variables are now required.  Previously, the
corresponding Django settings would default to 'gracedb'.

This will (hopefully) allow us to receive error emails from the
container deployments on AWS.

Add a logging handler for printing to stdout. For container
deployments, we remove all other logging handlers and use this
new 'console' handler only. The incantation for starting
gunicorn with supervisord now sends the access and error logs
to stdout.

Traefik can pass the subject and issuer in a 'cert-infos'
header, so I am adding an authentication backend to use that.

Non-priority production containers will use the master for
writes and a read-replica database for reads. This commit adds
functionality for getting the replica's information from
environment variables and sets up a database routing scheme.