- Cleanup, pimpl NotificationServer and Notification for export
- Wire the old dataengine up to use it for compat:
  it shows notifications but is otherwise pretty broken right now
- Start writing kconfigxt and Settings code (no real code yet)
- Add a Inhibition DBus interface (no actual server-side code yet)
- Group notifications by application
  Pretty much tasks grouping model from libtaskmanager slightly adjusted
- Let widget take full height when expanded in vertical panel "side bar usecase"
- Fix bugs here and there