Restructure

 * cups, firewall, shutdown, offline
    Moved into core
 * core
    Renamed to 'src'
 * xfce4, lightdm
    Moved into applications
 * applications
    Renamed to 'extra'
 * xfce4/themes/KaroshiClearlooks
    Moved into root

All directories named 'desktop' (for .desktop files) have been renamed to
'applications'

CUPS web interface shortcut has been moved to xfce4, since other DEs may
already have printer configuration tools available.