Add pp_job_authenticate_async() and pp_job_authenticate_finish() methods for authentication of PpJob. This commit also adds "auth-info-required" property to PpJob https://bugzilla.gnome.org/show_bug.cgi?id=758170
https://bugzilla.gnome.org/show_bug.cgi?id=748336
Update the Printer Jobs Dialog to match the current designs at https://wiki.gnome.org/Design/SystemSettings/Printers https://bugzilla.gnome.org/show_bug.cgi?id=755626