Create a common interface for different multi widgets to allow to substitute the `QmitkStdMultiWidget` in classes / functions that currently need a `QmitkStdMultiWidget`, but should work with the new `QmitkCustomMultiWidget`.
Is this reasonable, or should we strive to create a custom multi widget (editor) in a way that we can substitute the custom variant for the standard variant (and change all occurrences of std with custom)?