mitk::Image should use its own UID strategy and not the default own.
Reasoning: UID should be as close to dicom as possible.
- From now all mitk::Image should have an filled DICOM.0008.0018 (SOP Instance UID) property for all its z-position and timesteps. (If it does not exists through the loading process it will be generated (this will be done by ))
- The content of DICOM.0008.0018 will be hashed to generate the ID
- If, for any reason (evil!!), DICOM.0008.0018 does not exist, one would fall back to default uid generation