Relocate transfer function initialization into separate class

Actual behavior

• The transfer function initialization is hard coded within the Class

Expected behavior

• The initialization should be relocated into another class for more clearness

Cause of the bug

(How could this happen?, what went wrong?)

• The initialization was a temporary hack.

Proposed solution

(How do I plan to fix this? Other solutions?)

• It would be more clear to relocate the initialization into a separate class

Affected classes

(Which classes will be modified?, Which other classes/modules could be affected by the proposed change?)

• mitk\Core\Code\DataManagement\mitkTransferFunction

• mitk\Core\Code\DataManagement\mitkTransferFunctionInitializer

• mitk\Core\Code\Testing\mitkTransferFunctionTest
• mitk\Core\Code\Rendering\mitkVolumeDataVtkMapper3D

• mitk\Modules\MitkExt\Rendering\mitkGPUVolumeMapper3D

• mitk\Modules\QmitkExt\QmitkTransferFunctionGeneratorWidget

How will the bugfix get tested?

(unit test possible?, manual test necessary? how can it be tested?)

• The Transferfunction test will be modified to check if the Transferfunction still works