ENH: Move edited segmentation to the study of the master volume
In addition, a feature is added to warn the user about issues with DICOM export. Many users have asked why they could not export a segmentation, and the answer always was that because it was not under a patient+study. A check is now done when clicking Export to DICOM in subject hierarchy, and a warning is shown that briefly describes the issue and the solution if the exported node did not have the proper parents.