sane defaults → smart placement instead of cascade

[David Prieto]

Binary package hint: compiz

After using the "smart" option in the place plugin, I've found that it's much handier and makes better use of the screen state than "cascade", and it is far less irritating too. It's not the kind of thing that users are going to run to change because it gives no spectacular effects, but overall it makes the whole desktop experience more pleasant. So please, could it be active by default?