[Xmonad] darcs patch: merge old workspace tags with new on res... (and 1 more)

Here's a resend of my defaultLayout refactor amend-recorded to deal with a conflict. I think this'll make changes noticeably more painless for users (in particular layout transformers). David Wed Sep 26 14:33:09 EDT 2007 David Roundy * merge old workspace tags with new on restart. Thu Sep 27 22:02:08 EDT 2007 David Roundy * define defaultLayout in Config.hs.