The class was used as a base class for plugin views but has been replaced with `QmitkAbstractView`.
We should remove all the remnants of `QmitkFunctionality` (inside `Plugins\org.mitk.gui.qt.common.legacy\src\`).
As far as I can see the only classes that are not updated are `QmitkIGTTrackingDataEvaluationView` and `QmitkIGTTrackingSemiAutomaticMeasurementView`.
All other files only contain strings / references to the class but do not use it anymore.
Some classes inside rDIPP need to be checked as well.
(IMPORTANT) API breaking changes
- `QmitkIGTTrackingDataEvaluationView` does not subclass `QmitkFunctionality` anymore, but `QmitkAbstractView` instead
- the functions `MultiWidgetAvailable` and `MultiWidgetNotAvailable` are not available anymore
- `QmitkIGTTrackingSemiAutomaticMeasurementView` does not subclass `QmitkFunctionality` anymore, but `QmitkAbstractView` instead
- the functions `MultiWidgetAvailable` and `MultiWidgetNotAvailable` are not available anymore