Continue corner cases testcase
The check for cycles in composite relationships was only being done on commits to an existing persistent root, but not on the first commit. Do it on the first commit too.
-[COObject validateSingleValue:conformsToPropertyDescription:]: special case to support the case when we're using COObject class and not a user-supplied subclass
Factor out a -entityDescriptionForObject: method in COObject, to be moved to ETModelDescriptionRepository later
Remove
+ (ETEntityDescription *)newUnorderedReflexiveCompositeOneToManyEntityDescription;
from TestUnorderedCompositeRelationship.

Move it to FolderWithNoClass.h/m.
Merge pull request #8 from etoile/validate-object-graphs-on-first-commit

Validate object graphs for cycles in composites on first commit
Merge commit '15bbcc26eae0711bf267e629d6bf46dce29c05a1' into metamodel-corner-cases

Conflicts:
	Core/COObject.m
Update TestMetamodelCornerCases.m comments