Not tested but shouldn't break something

The Github link is just a redirect to Tulir's own GitLab, so I replaced the self-build link
The docker container repository was rearranged hierarchically (dock.mau.dev/tulir/mautrix-facebook -> dock.mau.dev/mautrix/facebook)
Tagged versions have been made available, thus :latest -> :v0.3.1

This adds https://github.com/matrix-org/matrix-doc/pull/2409 to the
appservice registrations, enabling synapse to push EDUs to appservices.

Fixes a regression introduced in f6097fbba1fb, which was cauing Synapse
to die with this error message:

> ValueError: sender_localpart needs characters which are not URL encoded.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/806

I had intentionally held it back in 39ea3496a4
until:
- it received more testing (there were a few bugs during the
migration, but now it seems OK)
- this migration guide was written

The `mobile` branch got merged to `master`, which ends up becoming
`:latest`. It's a "rewrite" of the bridge's backend and only
supports a Postgres database.

We'd like to go back (well, forward) to `:latest`, but that will take
a little longer, because:
- we need to handle and document things for people still on SQLite
(especially those with external Postgres, who are likely on SQLite for
bridges)
- I'd rather test the new builds (and migration) a bit before
releasing it to others and possibly breaking their bridge

Brave ones who are already using the bridge with Postgres
can jump on `:latest` and report their experience.

Fixes a problem like this:
> File "/usr/lib/python3.8/site-packages/mautrix/bridge/e2ee.py", line 79, in __init__
> raise RuntimeError("Unsupported database scheme")

mautrix-python's e2ee.py module expects to find `postgres://` instead of
`postgresql://`.

This makes the `sqlite://` URI match what we were using before
and what the config expects.

Looks like there are some that I missed in 087dbe4ddc

I was thinking that it makes sense to be more specific,
and using `_postgres_` also separated these variables
from the `_database_` variables that ended up in bridge configuration.

However, @jdreichmann makes a good point
(https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/740#discussion_r542281102)
that we don't need to be so specific and can allow for other engines (like MySQL) to use these variables.

Regression since 2d99ade72f and 9bf8ce878e94, respectively.

When SQLite is to be used, these bridges expect an `sqlite://`
connection string, and not a plain file name (path), like Appservice
Discord and mautrix-whatsapp do.

This also disables presence if it's disabled for Synapse.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/716

This patch makes us use more fully-qualified container image names
(either prefixed with docker.io/ or with localhost/).

The latter happens when self-building is enabled.

We've recently had issues where if an image was removed manually
and the service was restarted (making `docker run` fetch it from Docker Hub, etc.),
we'd end up with a pulled image, even though we're aiming for a self-built one.
Re-running the playbook would then not do a rebuild, because:
- the image with that name already exists (even though it's something
else)
- we sometimes had conditional logic where we'd build only if the git
repo changed

By explicitly changing the name of the images (prefixing with localhost/),
we avoid such confusion and the possibility that we'd automatically pul something
which is not what we expect.

Also, I've removed that condition where building would happen on git
changes only. We now always build (unless an image with that name
already exists). We just force-build when the git repo changes.

Related to #451 (Github Issue).

This keeps the roles cleaner and more independent of matrix-base,
which may be important for people building their own playbook
out of the individual roles and not using the matrix-base role.

I've been thinking of doing before, but haven't.

Now that the Whatsapp bridge does it (since 4797469383),
it makes sense to do it for all other bridges as well.
(Except for the IRC bridge - that one manages most of registration.yaml by itself)

We do use some `:latest` images by default for the following services:
- matrix-dimension
- Goofys (in the matrix-synapse role)
- matrix-bridge-appservice-irc
- matrix-bridge-appservice-discord
- matrix-bridge-mautrix-facebook
- matrix-bridge-mautrix-whatsapp

It's terribly unfortunate that those software projects don't release
anything other than `:latest`, but that's how it is for now.

Updating that software requires that users manually do `docker pull`
on the server. The playbook didn't force-repull images that it already
had.

With this patch, it starts doing so. Any image tagged `:latest` will be
force re-pulled by the playbook every time it's executed.

It should be noted that even though we ask the `docker_image` module to
force-pull, it only reports "changed" when it actually pulls something
new. This is nice, because it lets people know exactly when something
gets updated, as opposed to giving the indication that it's always
updating the images (even though it isn't).

We log to journald anyway. There's no need for double-logging.

It should not that matrix-synapse logs to journald and to files,
but that's likely to change in the future as well.
Because Synapse's logs are insanely verbose right now (and may get
dropped by journald), it's more reliable to have file-logging too.

As Synapse matures and gets more stable, logging should hopefully
get less, we should be able to only use journald and stop writing to
files for it as well.

Using a separate directory allows easier backups
(only need to back up the Ansible playbook configuration and the
bridge's `./data` directory).

The playbook takes care of migrating an existing database file
from the base directory into the `./data` directory.

In the future, we can also mount the configuration read-only,
to ensure the bridge won't touch it.
For now, mautrix-facebook is keen on rebuilding the `config.yaml`
file on startup though, so this will have to wait.

Related to #193, but for the Facebook bridge.
(other bridges can be changed to do the same later).

This patch makes the bridge configuration entirely managed by the
Ansible playbook. The bridge's `config.yaml` and `registration.yaml`
configuration files are regenerated every time the playbook runs.

This allows us to apply updates to those files and to avoid
people having to manage the configuration files manually on the server.

-------------------------------------------------------------

A deficiency of the current approach to dumping YAML configuration in
`config.yaml` is that we strip all comments from it.
Later on, when the bridge actually starts, it will load and redump
(this time with comments), which will make the `config.yaml` file
change.

Subsequent playbook runs will report "changed" for the
"Ensure mautrix-facebook config.yaml installed" task, which is a little
strange.

We might wish to improve this in the future, if possible.

Still, it's better to have a (usually) somewhat meaningless "changed"
task than to what we had -- never rebuilding the configuration.

Continuation of 54a281a425.
Related to #188 (Github Pull Request).