Add role prefix to role specifig variable to avoid conflicts when
using multiples role on the same machine on the same play.

- User last official deb package from matrix.org

- Revised LDAP integration:
  * ldap_server, ldap_domain [ ldap_basedn ] config vraiables.
  * Bind a protected service account with a service password and
    start-tls

- Hardcoded matrix.lilik.it --> {{ ansible_hostname }}.{{ domain }}

- Sqlite -> Postgres

New variables:

- matrix_domain | default($domain)