COPersistentRoot, COEditingContext: print a bit more detail in description methods to help with debugging (persistent root prints its root object entity name in -description, editing context prints all persistent roots in -detailedDescription)

git-svn-id: http://svn.gna.org/svn/etoile/trunk/Etoile/Frameworks/CoreObject@10203 7b3f36aa-e6db-49c1-8b4c-66eac1997e64
Add a sanity check that one side of a relationship is marked as derived.

git-svn-id: http://svn.gna.org/svn/etoile/trunk/Etoile/Frameworks/CoreObject@10204 7b3f36aa-e6db-49c1-8b4c-66eac1997e64