Use rofi-powermenu to show options for suspend,reboot, shutdown,
lockscreen, log out. Can be invoked with <M-backspace>. Other power
option shortcuts have been removed from quick access through sxhkd or
i3. Lockscreen can still be quickly set with <M-x>.
Lockscreen now resides in its own script to provide one source of truth,
and in case it is further customized in the future.
