Label comparison fails.

Labels are created manually in the test but they miss the DICOM properties of labels that were created when creating a LabelSetImage. That's why they differ recently. Such DICOM properties should also be added right in the constructor of a label.

Side note: when I looked through the code it seems that some of the DICOM properties should always be in sync with common properties like "name". However, they are not, as all the set methods of the common properties do not update the DICOM properties as well. When two or more properties are meant to be synchronous, property aliases (a property core service) is a good solution to have only a single source of truth.