Summary of bug description
   * actual behaviour
   MouseWheel event has no information about the wheel movement
   The current WheelEvent "class" is just a typedef on a DisplayPositionEvent   
   * expected behaviour
   MouseWheel event has the information about the wheel movement   
 
Cause of the bug
In different requirements we need the mouse wheel movement for interaction.

Proposed solution
Implement a class mitkWheelEvent derived from mitkDisplayPositionEvent which has the additional information about the mouse wheel movement. 

Affected classes

QmitkEventAdapter
mitkEventTypedefs
mitkWheelEvent

How will the bugfix get tested?
manual test: use the mouse wheel in an interaction with a statemachine which uses action id 105.