Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/570

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/641

Fixes #685 (Github Issue).

Fixes #586 (Github Issue)

Listen 8448 directive makes apache listen on that port, without it federation does not work.

Invitations weren't working for me until I added 'nocanon' to these additional places. Until then, invitations failed with "Invalid signature for server ..." errors, as in https://github.com/matrix-org/synapse/issues/3294 .

I didn't check whether the user_directory/search proxy line also needs it, I just assumed it should have it too.

The other two proxy lines in this example also include a 'retry=0' parameter. That's a separate issue; I haven't touched it here.

Thanks to @ralfi!

Contributed by @ralfi.

Putting a lot of comments inbetween `[matrix-servers]` and the example
host line may make someone decide to clean up the comment
and accidentally skip-over the `[matrix-servers]` part.

Discussed in #121 (Github Issue).

Related to #121 (Github Issue)

Continuation of 1f0cc92b33.

As an explanation for the problem:
when saying `localhost` on the host, it sometimes gets resolved to `::1`
and sometimes to `127.0.0.1`. On the unfortunate occassions that
it gets resolved to `::1`, the container won't be able to serve the
request, because Docker containers don't have IPv6 enabled by default.

To avoid this problem, we simply prevent any lookups from happening
and explicitly use `127.0.0.1`.

This supersedes #59 (Github Pull Request),
which was greatly beneficial in creating our sample Apache configuration.

With this change, the following roles are now only dependent
on the minimal `matrix-base` role:
- `matrix-corporal`
- `matrix-coturn`
- `matrix-mailer`
- `matrix-mxisd`
- `matrix-postgres`
- `matrix-riot-web`
- `matrix-synapse`

The `matrix-nginx-proxy` role still does too much and remains
dependent on the others.

Wiring up the various (now-independent) roles happens
via a glue variables file (`group_vars/matrix-servers`).
It's triggered for all hosts in the `matrix-servers` group.

According to Ansible's rules of priority, we have the following
chain of inclusion/overriding now:
- role defaults (mostly empty or good for independent usage)
- playbook glue variables (`group_vars/matrix-servers`)
- inventory host variables (`inventory/host_vars/matrix.<your-domain>`)

All roles default to enabling their main component
(e.g. `matrix_mxisd_enabled: true`, `matrix_riot_web_enabled: true`).
Reasoning: if a role is included in a playbook (especially separately,
in another playbook), it should "work" by default.

Our playbook disables some of those if they are not generally useful
(e.g. `matrix_corporal_enabled: false`).

Adds support for managing certificates manually and for
having the playbook generate self-signed certificates for you.

With this, Let's Encrypt usage is no longer required.

Fixes Github issue #50.