Show '...' when shutdown/restart/logout confirmations should be shown

Binary package hint: indicator-session

When these confirmations should be shown the corresponding menu entries should be suffixed with '...'.

I already implemented a part of that in the patch attached to bug 419472.

It is only missing to switch whether the dots should be shown or not at runtime when the gconf key has been changed.

Currently there is a restart required to change the menu according to the gconf key.

This means if the system starts and the confirmations are activated in gconf then the three dots are shown but when now
the confirmations are disabled in gconf the three dots are still shown. (And vice versa of course). A restart of the system is then
required to make the menu update and the three dots disappear. However, if the confirmations just have been disabled in gconf the three dots are incorrectly still shown but the confirmations correctly are not shown any longer. This might be confusing.