Fix gitlab issue 69 - wrong offset of newly created ITD

Fix for #69 (closed), also added handling for offset correction of InteroperabilityIFD tag when new tags are inserted. Before this the InteroperabilityIFD offset was unchanged and the block was therefore broken afterwards.

Just as mentioned in the previous merge requests, some unrelated CI checks do currently fail, fixes are already contained in Merge Request !56 (merged), so I don't added them again to prevent merge conflicts.