Make titles more consistent

This patch aims to bring config reference titles more consistents
to let the user understand the structure at a first glance.

backport: havana

Change-Id: I163e508621c7a46c753836a4743b32af25acf011
Signed-off-by: Emilien Macchi <emilien.macchi@enovance.com>
(cherry picked from commit 6fbbae2dce5127169892970f9c1ddd13c88215fe)
Merge "Make titles more consistent" into stable/havana