Redesign per-event config in notifications KCM
Currently the notifications KCM has the "Configure Events..." button that opens a dialog window with fine-grained settings.
That dialog is kind of odd UX-wise. This was mostly laziness during the KCM QML port by keeping the existing dialog from KNotifyConfig. Another part of the reason was that the dialog was somewhat complex with lots of types of possible actions.
We recently slimmed down these actions so only "Show a message in a popup" and "Play a sound" remain.
We should fold the UI for these into the main KCM view and get rid of the extra dialog