Continuation of #246 (Github Pull Request)

Related to #223 (Github Pull Request)

ef5e4ad061 intentionally makes us conform to
the logging format suggested by the official Docker image.

Reverting this part, because it's uglier.

This likely should be fixed upstream as well though.

Somewhat related to #213 (Github Pull Request).

We've been moving in the opposite direction for quite a long time.
All services should just leave logging to systemd's journald.

This is a new feature of Synapse v1.1.0.

Discussed in #145 (Github Pull Request).

Using `|to_json` on a string is expected to correctly wrap it in quotes (e.g. `"4"`).
Wrapping it explicitly in double-quotes results in undesirable double-quoting (`""4""`).

Bridges start matrix-synapse.service as a dependency, but
Synapse is sometimes slow to start, while bridges are quick to
hit it and die (if unavailable).

They'll auto-restart later, but .. this still breaks `--tags=start`,
which doesn't wait long enough for such a restart to happen.

This attempts to slow down bridge startup enough to ensure Synapse
is up and no failures happen at all.

Attempt to fix #192 (Github Issue), potential regression since
70487061f4.

Serializing as JSON/YAML explicitly is much better than relying on
magic (well, Python serialization being valid YAML..).
It seems like Python may prefix strings with `u` sometimes (Python 3?),
which causes Python serialization to not be compatible with YAML.

Fixes #171 (Github Issue).

Reasoning is the same as for matrix-org/synapse#5023.

For us, the journal used to contain `docker` for all services, which
is not very helpful when looking at them all together (`journalctl -f`).

Use Jinja2 lstrip_blocks option in templates to ensure consistent
indentation in generated files.

This prevents Ansible from sometimes failing to decrypt vault variables

- matrix_enable_room_list_search - Controls whether searching the public room list is enabled.
 - matrix_alias_creation_rules - Controls who's allowed to create aliases on this server.
 - matrix_room_list_publication_rules - Controls who can publish and which rooms can be published in the public room list.

Doing this for consistency.

Related to #117 (Github Pull Request).

This allows overriding the default value for `include_content`. Setting
this to false allows homeserver admins to ensure that message content
isn't sent in the clear through third party servers.

`matrix_synapse_no_tls` is now implicit, so we've gotten rid of it.

The `homeserver.yaml.j2` template has been synchronized with the
configuration generated by Synapse v0.99.1 (some new options
are present, etc.)

This reverts commit 536c85619f.

Looks like binding metrics on IPv6 (`::`) fails with an error:

socket.gaierror: [Errno -2] Name does not resolve

For consistency with all our other listeners,
we make this one bind on the `::` address too
(both IPv4 and IPv6).

Additional details are in #91 (Github Pull Request).

Docker apparently doesn't like IPv6.