QML needs it on the model it uses (Notifications) where they used to be but GammaRay seems to be taking them from the source (NotificationsModel).
This has both models (and jobs model) return the roleNames() and moves them to Utils so they're shared.

• Notifications still work
• Inspecting the models with GammaRay has proper role names now.

I kinda would have expected the rolenames from notificationsmodel to bubble down to us but maybe qml asks for them before we have initialized the models