CCAR: add automatic management of GenericObj in study.

CCAR: add automatic management of GenericObj in study.
If a GenericObj id publish in study, its reference count must be incremented (call to Register()).
When it is unpublished, its reference count must be decremented (call to Destroy()).
This was not done when calling SetValue on a AttributeIOR so if someone manages
GenericObj in the right way, the references in study could be lost.