implementation of join statements for predicates operating on toMany relationships

Hi

My first commit adds handling of toMany relationships in join statement construction.
The second one is very related as it adds handling (a rather naive one) of ANY in NSPredicate.
Original core data store enforces using of ANY (or other NSComparisonPredicateModifier?) in case of NSPredicate operating on toMany relationship. Here I've just added DISTINCT to selection, when ANY is used. It works for my case , but probably needs more testing to check if applicable in all cases...

Best regards
Rafal