Add chrony service
Also, do not build and add ntp to the system unless it is enabled.
chrony: properly set rtconutc option, and add a few more options
atop: Add basic config option for /etc/atoprc
Merge pull request #170 from wizeman/atop

atop: Add basic config option for /etc/atoprc
Merge pull request #169 from wizeman/chrony

Add chrony service
gnunet: it was missing extraGroups
Set the domain name of the machine

The domain name was not being set before, even if the administrator
properly configured the networking.domain option in
/etc/nixos/configuration.nix.
openvpn.nix: Use systemd.*

Also add an option ‘autoStart’ to configure whether an OpenVPN
instance should be started automatically.  And don't log to
/var/log/openvpn-* anymore.
apparmor: Fix broken iputils/ping profile
apparmor: Fix loading multiple profiles

apparmor's systemd service wasn't working when multiple profiles were
defined, due to the ExecStart commands in the service file being
broken into multiple lines, instead of being separated by ';'.
apparmor: Fix service stop

When stopping the apparmor service, the profile removal failed with
parsing errors due to not including the
${pkgs.apparmor}/etc/apparmor.d directory.
add networkmanager_openvpn to systemPackages
Merge pull request #172 from wizeman/apparmor-ping

apparmor: Fix broken iputils/ping profile
Merge pull request #173 from wizeman/apparmor-service

Apparmor service fixes
Merge pull request #167 from wizeman/domain

Set the domain name of the machine
Generate /etc/passwd and /etc/group statically
Add users.mutableUsers, to allow using useradd command. WIP, doesn't work at all yet.