Imspector OBF: support version 5 stacks

See http://www.openmicroscopy.org/community/viewtopic.php?f=4&t=7698.  Without this change, the data file attached to the forum thread will throw an exception on opening/importing.  With this change, there should be several images, each with quite a bit of original metadata.

No additional testing is needed besides checking that builds remain green.