Strings addition and UI change in g-s-d/printing

[Marek Kasik <mkasik redhat com>]

Hi,

I've pushed a new notification to gnome-settings-daemon. It informs user 
that a print job which needs authentication was sent to a printer (see 
https://bugzilla.gnome.org/show_bug.cgi?id=766563#c10). Clicking on it 
will open gnome-control-center's Printers panel with opened Jobs dialog 
where user can authenticate such jobs.

The new strings are:

"%s Requires Authentication"
"Credentials required in order to print"

The freeze exceptions were approved by Piotr Drąg, Alexandre Franke, 
Michael Catanzaro and Olav Vitters.

Thank you all for your help with this and I'm sorry for such late addition

Marek