Warn about "Orphaned" KLV Sets

[thomasheritage]

Warnings are given about Dark KLV Sets and Properties.

However, it seems that KLV Sets which are known about (and appear within the Header Metadata of the MXF file) but which are "orphaned" don't get mentioned. It would be helpful for these to appear in the output somewhere. "Orphaned" here means that they are not strongly referenced by anything.

An example file is here (you need a free IRT login):
http://mxf.irt.de/files/download.php?action=getFile&repository=golden&id=229

This MXF file seems to have been built with the thought that the "AnnotationParticipants" Element contains StrongReferences to "Participants". The Reg-XML file shows that this Element contains a set of Instance IDs of three "Participant" Objects which are in the MXF file. However, this Element actually has the Type "ParticipantGlobalReferenceSet" which is a set of WeakReferences. This means that the three "Participant" Objects in the MXF file are orphaned and do not appear anywhere in the Reg-XML output. Probably a warning should be provided by the software; perhaps the orphaned Objects should even be rendered as Reg-XML and included inside a comment in the output XML (somewhere near the end) in the same way as Dark items.