Extend GridSelect navigation
Extend GridSelect navigation

Ignore-this: f2d279b8e46e6eaf3477fdc5cf77be63
Add moveNext and movePrev, which move selection to next/previous item.

darcs-hash:20110515154246-c5067-e117b3d5753e868963b36a10d2e17ccc427a97b7

yzhou61/xmonad-contrib,yzhou61/xmonad-contrib,yzhou61/xmonad-contrib