Rename 'spawnStatusBarAndRemember' and 'cleanupStatusBars', made them command specific
Rename 'spawnStatusBarAndRemember' and 'cleanupStatusBars', made them
command specific

- The names were awfully long. spawnStatusBar and killStatusBar are
perfectly fine alternatives.
- It's more flexible to have killStatusBar command specific. Also added
killAllStatusBars to provide the old functionality

xmonad/xmonad-contrib,xmonad/xmonad-contrib