To be able to shutdown or reboot your system, you'll have to add a .pkla file
in %%LOCALBASE%%/etc/polkit-1/localauthority/50-local.d directory. Which looks
like this (replace PUTYOURGROUPHERE by your group):

[Restart]
Identity=unix-group:PUTYOURGROUPHERE
Action=org.freedesktop.consolekit.system.restart
ResultAny=yes
ResultInactive=yes
ResultActive=yes

[Shutdown]
Identity=unix-group:PUTYOURGROUPHERE
Action=org.freedesktop.consolekit.system.stop
ResultAny=yes
ResultInactive=yes
ResultActive=yes