Fixes #155 (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`).

The goal is to move each bridge into its own separate role.
This commit starts off the work on this with 2 bridges:
- mautrix-telegram
- mautrix-whatsapp

Each bridge's role (including these 2) is meant to:

- depend only on the matrix-base role

- integrate nicely with the matrix-synapse role (if available)

- integrate nicely with the matrix-nginx-proxy role (if available and if
required). mautrix-telegram bridge benefits from integrating with
it.

- not break if matrix-synapse or matrix-nginx-proxy are not used at all

This has been provoked by #174 (Github Issue).

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

This reverts commit 172d59ba05.

This prevents Ansible from sometimes failing to decrypt vault variables

As discussed in #151 (Github Pull Request), it's
a good idea to not selectively apply casting, but to do it in all
cases involving arithmetic operations.

Previously, we'd show an error like this:

{"changed": false, "item": null, "msg": "Detected an undefined required variable"}

.. which didn't mention the variable name
(`matrix_ssl_lets_encrypt_support_email`).

Looks like we may not have to do this,
since 1.4.2 fixes edge cases for people who used the broken
1.4.0 release.

We jumped straight to 1.4.1, so maybe we're okay.
Still, upgrading anyway, just in case.

Use matrix_docker_network and matrix_base_data_path in matrix-remove-all
instead of hardcoded default values.

Use an int conversion in the computation of the value of
matrix_nginx_proxy_tmp_directory_size_mb, to have the integer value
multiplied by 50 instead of having the string repeated 50 times.

It doesn't hurt to attempt renewal more frequently, as it only does
real work if it's actually necessary.

Reloading, we postpone some more, because certbot adds some random delay
(between 1 and 8 * 60 seconds) when renewing. We want to ensure
we reload at least 8 minutes later, which wasn't the case.

To make it even safer (in case future certbot versions use a longer
delay), we reload a whole hour later. We're in no rush to start using
the new certificates anyway, especially given that we attempt renewal
often.

Somewhat fixes #146 (Github Issue)

The code used to check for a `homeserver.yaml` file and generate
a configuration (+ key) only if such a configuration file didn't exist.

Certain rare cases (setting up with one server name and then
changing to another) lead to `homeserver.yaml` being there,
but a `matrix.DOMAIN.signing.key` file missing (because the domain
changed).
A new signing key file would never get generated, because `homeserver.yaml`'s
existence used to be (incorrectly) satisfactory for us.

From now on, we don't mix things up like that.
We don't care about `homeserver.yaml` anymore, but rather
about the actual signing key.

The rest of the configuration (`homeserver.yaml` and
`matrix.DOMAIN.log.config`) is rebuilt by us in any case, so whether
it exists or not is irrelevant and doesn't need checking.