PK: Improve information on resources that extend others

There's the possibility that resources will extend another. In these
cases often the resource name isn't overly useful. For example
org.gnome.Software.Plugin.Steam title is "Steam Support" or
org.kde.discover.flatpak is "Flatpak backend".
Concatenate therefore, concatenate the extended resource first: "Plasma
Discover - Flatpak backend".