If the playbook were to run with `--tags=setup-nginx-proxy`,
it wouldn't go into `setup_corporal.yml`, which meant it wouldn't
perform a bunch of `set_fact` calls which override important
nginx proxy configuration.

We run these variable overrides on each call now (tagged with `always`)
to avoid such problems in the future.

We've been using Goofys for a long time instead.

Since cbee084ac19b6, this playbook supports Postgres 10.x,
but keeps existing Postgres-9.x installs on 9.x.

This playbook can now also be ran with `--tags=upgrade-postgres`
to make it upgrade from Postgres 9.x to 10.x (or other versions
in the future).

Switching from from avhost/docker-matrix (silviof/docker-matrix)
to matrixdotorg/synapse.

The avhost/docker-matrix (silviof/docker-matrix) image used to bundle
in the coturn STUN/TURN server, so as part of the move,
we're separating this to a separately-ran service
(matrix-coturn.service, powered by instrumentisto/coturn-docker-image)

Improves performance of media store operations.

It was never intended to be there, but was while testing/development
and got forgotten later.

Doing this means that matrix-nginx-proxy now starts
occupying port 80, which necessitates that
SSL renewal happens slightly differently.