[Xmonad] darcs patch: move Layout stuff into class (hokey firs... (and 2 more)

Here, just as a demonstration, I add a Show instance to the Layout class. This is by far the easy part, a Read instance is far more tricky, requiring that SomeLayout know the types of all possible layouts, which of course, wreaks havoc with configurability and modularity. David Fri Sep 14 17:59:59 EDT 2007 David Roundy * move Layout stuff into class (hokey first cut). Thu Sep 20 11:52:37 EDT 2007 David Roundy * eliminate ugly OldLayout. Thu Sep 20 12:12:08 EDT 2007 David Roundy * add Show instance to Layout