power management: do not shutdown on pressing power button
xfce4-session now handles calling xfce4-logout correctly when the power button is pressed
reverts commit fb46446
skel: openbox: various fixes/tweaks
 * decrease number of workspaces to 2
 * fix keybord shortcuts for screenshots
 * remove buggy keyboard shortcut
 * do not chnage workspace when scrolling the mouse wheel on the desktop (fixes #50)
 * do not send window to bottom on Shade (#fixes #50)