Fixed -allPropertyDescriptions cache invalidation issues (this was causing 
a test failure).

When the cache is invalidated in a parent entity, all the subentities now 
treat their cache as invalid.

Note: The performance is the same as previously. For code simplicity, we 
recache all parent entities when recaching a subentity.


git-svn-id: http://svn.gna.org/svn/etoile/trunk/Etoile/Frameworks/EtoileFoundation@10176 7b3f36aa-e6db-49c1-8b4c-66eac1997e64