Summary of bug description
  
Originally:
MITK crashes on close after InteractiveSegmentation has been closed
    
 
Cause of the bug
Varying event/observer mechanisms lead to calls to objects that were already destroyed. 
QmitkSlicesInterpolator and QmitkDataStorageComboBox do not destroy those callbacks at their own destruction.

Proposed solution
remove observer/event connections on object destruction

Affected classes
see patch

How will the bugfix get tested?
Verified by several bundle/application tests. I closed several bundles after loading different images and then I closed the application.