Support writing a 16bit 3D image to a single DICOM file

Request from the mailing list:

When I try to save an 8bit 3D image to a single DICOM file using ITK/GDCM, it succeeds. A suitable SOP class (Multi-frame Grayscale Byte Secondary Capture Image IOD) is assigned to the DICOM image. The same code fails when the image is 16bit, though DICOM standard does seem to have a suitable SOP class (Multi-frame Grayscale Word Secondary Capture Image IOD) for the 16bit image.

Start by locating the ITK/GDCM path that writes an 8-bit 3D image to one DICOM file, then compare how the 16-bit case is handled. Verify the Multi-frame Grayscale Word Secondary Capture Image IOD path and confirm that a 16-bit 3D image can be written successfully as a single DICOM file.

Written by the indexing model from the issue text.