[xmonad] ScratchWorkspace

I've just pushed in a ScratchWorkspace module that defines a scratch workspace. You can look at Config.Droundy to get an idea how to use it (as it's undocumented). It's still very crude, and anyone who wants to take a shot at cleaning it up is welcome to try. The main issue is that the scratch workspace is available as a "normal" workspace, which I find a little annoying. I'd prefer it remained hidden until I asked for it. But I can't quite see how to do that, either. Enjoy! (and comments/suggestions are welcome, although I've really already wasted more time on this than I ought...) -- David Roundy Department of Physics Oregon State University