The main service configuration (/etc/$project/$project.conf) can still be used
for configuration but the preferred way is to add config file snippets into
/etc/$project/$project.conf.d/ instead.

As part of the packaging, the package itself installs a config snippet at
/etc/$project/$project.conf.d/010-$project.conf with basic configuration. This
file should not be modified. In case there is a need to overwrite or add
settings, a XXX-$project.conf (XXX being a 3 digit number) should be created
instead.

Config directory file snippet naming should follow these conventions:
- snippets should start with "XXX-" where "X" is a number
- snippets must end with ".conf"
- config management systems (Crowbar, Salt, ...) should use numbers
  between 100 and 499
- users should use numbers starting from 500

Configuring just a single $program (eg for Nova, $project is "nova" and
$program is "nova-api", "nova-compute", "nova-scheduler", ...) can be done
in a similar way. The config snippets should be placed in
/etc/$project/$program.conf.d/ . The same snippets rules apply here, too.

$program reads the configuration files in the following order:
- /etc/$project/$project.conf
- /etc/$project/$project.conf.d/*.conf (lexically sorted)
- /etc/$project/$program.conf.d/*.conf (lexically sorted)

The last configured key overwrites all previous ones. In particular, settings
in /etc/$project/$project.conf are overwritten by config values from any file
in /etc/$project/$project.conf.d/XXX-$project.conf .