ENH: JPEG IO now writes and reads spacing, similar to the TIFF IO (ITK-3023)

Change-Id: I5f40e226040233672eed3dcdec1a5b9007899574
Merge topic 'ITK-3023'

b7c7107 ENH: JPEG IO now writes and reads spacing, similar to the TIFF IO (ITK-3023)