* src/gdcmDocument.cxx: wrong type on return fixed (thanks dashboard)

  * src/gdcmDocument.cxx: wrong type on return fixed (thanks dashboard)
  * CLEANUP_ROUND (14) for gdcmPixelConvert
    - PixelConvert::GetLutRGBA(FILE*) is now GetLutRGBA() (no fp needed)
    - PixelConvert::BuildRGBImage()(FILE*) is now BuildRGBImage() (no fp needed)
    - File::GetImageDataIntoVector() doesn't need unnecessary OpenFile() and
      CloseFile() anymore.
    - File::GetImageDataRaw() doesn't call GetImageDataIntoVectorRaw()
      anymore and hence avoids storing a copy of PixelConvert::Decompressed
      into File::Pixel_Data.