#22 Descriptor category in CDCI codec.

[Jim Trainor]

The IAAFPlugin::CreateDescriptor implementation in the
CDCI codec sets the category class to
AUID_AAFDefObject.

The JPEG, WAVE, and CDCI codecs all set their
categories to AUID_AAFCodecDef.

AUID_AAFDefObject is an abtract class type. If
something tries to create that object type it will fail (not
sure if anything actually does that). If that is not a
problem, then it would still be good to clean up the
inconsistency between the implementations.