Kiosk mode? Disable Ctrl-Alt-Delete

[Adam Tauno Williams <awilliam whitemice org>]

I'm part of a group that is attempting to build a kiosk-like solution on
boxes running GNOME3.  We are very close.  And with the gsettings
lockdown options the system can be pretty well secured.

But is there any setting to disable Alt-Tab & Alt-` ?

All the menus, etc... can be eliminated an the application run in 'true'
full-screen but the overview mode can still be activated and application
switching performed.