Add a section to the "Integration topics" chapter about how we integrate
systemd. Add a first subsection about how dbus and dbus-broker work with
systemd.
This is just the start of the integration information about systemd.
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
