string additions in gnome-shell

[Matthias Clasen <matthias clasen gmail com>]

I just pushed a change to gnome-shell that adds a few new strings for
a variant of the restart dialog when offline updates are pending.

See

https://git.gnome.org/browse/gnome-shell/commit/?id=a0fa9937ba0ae8ed961bab8e9471ad569c5ae652

for the change, and

https://dl.dropboxusercontent.com/u/5031519/system-settings/end-session-dialogs.png

for the mockup of the dialog.