The use of the `QmitkMxNMultiWidget` is currently not possible due to different render window names.
In many cases hard-coded names like `"stdmulti.widget0"`, `"stdmulti.widget1"` etc. were used, which do not necessarily exist anymore when using the mxnMultiWidget.
The following list contains classes that have these hard-coded names and need to be refactored:
[x] `QmitkSliceBasedInterpolatorWidget`
[] `QmitkSlicesInterpolator`
- has partially been refactored
[x] `QmitkSurfaceBasedInterpolatorWidget`
[x] `PaintbrushTool`
[x] `QmitkToolSelectionBox`