sysadmin/selinux: improve commands to generate the interface file

Signed-off-by: Nicolas Iooss <nicolas.iooss_git@polytechnique.org>
Add Collectd documentation

Signed-off-by: Nicolas Iooss <nicolas.iooss_git@polytechnique.org>
web/php: document Apache and Nginx configurations

Signed-off-by: Nicolas Iooss <nicolas.iooss_git@polytechnique.org>