Add standard method to display explanatory text at the top of a KCM
Quite a few KCMs have some kind of explanatory text at the top of them to help users understand what the KCM does. Examples include:
- User Feedback
- Desktop Effects
- Screen Edges
- Touchscreen Gestures
- Legacy X111 Apps
- Night Color
And many other KCMs could really benefit from this, such as Activities, Global Themes, Window Rules, KWin Scripts.
Given this, it might make sense to add a standard method to do this, perhaps to AbstractKCM in KDeclarative. We would want to make SimpleKCM a subclass of AbstractKCM so it only has to be implemented once.