The previous implementation of the panel was unable to individually
update a PpPrinterEntry jobs count and its PpJobsDialog.
These changes make the job notifications trigger updates in the
PpPrinterEntry UIs, keeping track of job events on the go.
https://bugzilla.gnome.org/show_bug.cgi?id=779079
This commit introduces the following regressions:
- no possibility of renaming properties such as printer names,
location, or changing model/driver. This issue is going to be
solved nextly by the introduction of the PpDetailsDialog.
https://bugzilla.gnome.org/show_bug.cgi?id=767600