Disable shutdown and restart in indicator-session

Disable the "shutdown" and "restart" menu items in indicator-
session, because doing that while you're logged in inside the
chroot wedges your session.  (Unity dies, as does everything except
your gnome-terminal, and your session is stuck in "Ending" state)

Also, let lightdm invoke "reboot" via sudo without a passwd

Add dconf keys and locks to disable the user-background for
the unity-greeter (aka the lock screen), force the background
to MIT, and set a custom "logo" in the bottom right
Workaround GRUB's lack of LVM support

GRUB displays a spurious error message when recordfail support
is enabled and / is on an LVM partition.  (Trac: #1512)
Workaround this by scribbling over the function definition, thus
disabling the functionality, because we don't care.