TODO:

 * Implement the low power changed signal
 * Throw dbus errors when we fail dbus methods: org.gnome.PowerManager.NotInhibited.
 * Make strings more translatable
 * Integrate g-p-m with more modules, e.g. nautilus.
 * Give the user the ability to force an Inhibit()'d action
 * use the updated hal can_suspend_to_disk keys

 * Make new dbus interface (backwards compat):
- org.gnome.PowerManager.Inhibit.RequestCookie
- org.gnome.PowerManager.Inhibit.ClearCookie
- org.gnome.PowerManager.Inhibit.GetRequests
- org.gnome.PowerManager.Dpms.SetMode
- org.gnome.PowerManager.Dpms.GetMode
- org.gnome.PowerManager.BrightnessLcd.SetPercentage
- org.gnome.PowerManager.BrightnessLcd.GetPercentage
- org.gnome.PowerManager.BrightnessLcd.GetLevels
- org.gnome.PowerManager.Processor.SetGoverner
- org.gnome.PowerManager.Processor.GetGoverner
- org.gnome.PowerManager.Policy.CanSuspend
- org.gnome.PowerManager.Policy.CanHibernate
- org.gnome.PowerManager.Policy.CanShutdown
- org.gnome.PowerManager.Policy.CanRestart
- All have path of /org/gnome/PowerManager and org.gnome.PowerManager service.
