Allow a few parts of Riot config.json to be configured (#24)

Disable TLS 1.0

This also raises the default from 5 seconds to 15 seconds.

Regression since 3fd6fd647f

Allow specifying which parts of the role run from playbooks

Pretty much all variables live in their own `matrix_<whatever>`
prefix now and are grouped closer together in the default
variables file (`roles/matrix-server/defaults/main.yml`).

Update riot-web (0.17.0 -> 0.17.3)

It should be `/bin/mkdir` and `/bin/chown` on Ubuntu 18.04 for example.
Still, it doesn't seem like we need to create and chown these
directories at all, since the playbook takes care of creating them
and setting appropriate permission by itself.

Mautrix whatsapp

Regression since 67a445a74a

It's been incorrect since 23e4a473

Expose mautrix-telegram public endpoint through nginx

It used to allow user to logging with their own account to the bot
see: https://github.com/tulir/mautrix-telegram/wiki/Authentication#replacing-telegram-accounts-matrix-puppet-with-matrix-account
for more informations

Add DNS records table

Add sample .well-know config for Caddy

Add missing tag to task

The setup-all should include the setup_well_known task as well

Fix link to using your own webserver

We skipped v0.33.6 because of matrix-org/synapse#4014,
but v0.33.7rc2 fixed the problem.

If a network like `matrix-whatever` already exists for some reason,
the `docker_network` module would not create our `matrix` network.
Working around it by avoiding `docker_network` and doing it manually.

Fixes Github issue #12