Add Docker Network for matrix-mautrix-telegram-db ...

Postgres setup like
matrix_mautrix_telegram_configuration_extension_yaml: |
  appservice:
    database: "postgres://XXX:XXX@matrix-postgres:5432/mxtg"

 will fail without the right Dockernetwork

`/etc/nginx/conf.d/default.conf` was previously causing
some issues when used with our `--user`.

It's not the case anymore, so we can remove it.

Fixes #369 (Github Issue).

added matrix-sms-bridge

because the tty port will change

Remove hardcoded paths to commands on the host machine

Synapse v.1.14.0

Depending on the distro, common commands like sleep and chown may either
be located in /bin or /usr/bin.

Systemd added path lookup to ExecStart in v239, allowing only the
command name to be put in unit files and not the full path as
historically required. At least Ubuntu 18.04 LTS is however still on
v237 so we should maintain portability for a while longer.

fix for importing sqllite database

the current version fails the import, because the volume for the media is missing. It still fails if you have the optional shared secret password provider is enabled, so that might need another mount. Commenting out the password provider in the hoimeserver.yaml during the run works as well.

Clarify documentation on port forwarding of Jitsi/TRP behind NAT