I should be able to check containment of Sets in Sets

(User Story, Closed -> Fixed, Priority: Critical, Test Status: Unit tested , Reported By Justin du Coeur, )

Summary: It's common to want to ask, "Are any of the following values found in here?" or "Are all of the following values found in here?". Currently, this is doable, but kind of a pain.

I'm dealing with this by enhancing _contains() to be smarter. Currently, it only checks the first element of the value to test against, which is a warning sign to begin with. Now, if you give it a collection, it will check whether any of the values are present -- the generalization of the old behavior. And if you add the parameter all=true, it will require that all of the values be present.