I have mostly a pretty clean kde4 f15 system. Naturally, I am intrigued by Gnome3. I know that I could groupinstall gnome, but I don't want any of that old gnome2 cruft. How can I get just gnome3? How can I add a gnome entry into kdm, so that I can select (without changing my kde default, of course: I'm seeing the sights at a foreign port, not jumping ship)?