* FIX : now, the DocEntries are all deleted in the gdcmElementSet.

   * FIX : now, the DocEntries are all deleted in the gdcmElementSet.
     Two problems appear when doing it :
      - with the gdcmFile : when the GetImageData method is called, the pixels
        are stored in the gdcmPixelConvert, but a gdcmBinEntry link to these
        datas (pixels). And each structure destruct the datas when it's
        destructed. So we have two destructions for the same datas. To solve it,
        a flag is added in the gdcmBinEntry to indicate if the BinEntry owns the
        datas or not. If it doesn't own datas, then they will not destroyed by
        the gdcmBinEntry.
      - with the gdcmDicomDir : the sequences (gdcmSQItem) contain DocEntry
        elements. The DicomDir* (DicomDirPatient, etc.) inherit from SQItem.
        Thus destruct the DicomDir* elements and the TagHT of the ElementSet
        create a double destruction of the same DocEntry's. So, to solve it,
        the TagHT is simply cleared and the DicomDir* elements are destroyed.
   * TODO : add an entry concerning memory leaks in the DicomDir
   -- BeNours