Summary of bug description
   * actual behaviour
		Swaping a point upwards (pointSet->SwapPointPosition) removes the former point on the position.
		Swaping a point downwards removes the next point on the position.

   * expected behaviour
		swaping upwards: point at position 1 is at position 0 AND point at position 0 is at position 1
		swaping downwards: point at position 0 is at position 1 AND point at position 1 is at position 0
 
Cause of the bug
	wrong imlementation

Proposed solution
keep both points and write them back

Affected classes
mitkPointSet.cpp and header (method has no doxygen documentation)

How will the bugfix get tested?
tested in mitkPointSetTest