With minimization mostly hidden in GNOME 3, the control-alt-d shortcut is dramatic and confusing to a user if they hit it accidentally. We should take it out of the defalt set.

[ I don't see alt-f9 as so much of a problem: it's further away from common application shortcuts, and recovering one window from the overview is a lot simpler than recovering all your windows. ]

Marking ui-review in case we want to try and identify other shortcuts than need to be reviewed/changed as well, but this one should go at a minimum.