The previous code was leaking a string (job title), used an integer pointer
instead of an integer for an id and requited a lot of memory management for a
string array. There was a lot of boilerplate code required for property
management which was not being used much. This is why type safe methods are a
much better idea than GObject properties. :)
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
