LPS-35870 PermissionSubscription Javadoc

Hi Ray,

Could you review these Javadoc changes?

Cody added re-added the Javadoc and wordsmithed.

I elaborated on the case of using a subscription entity and inferred entity (contained within the subscription entity) and the case of a subscription entity being the inferred entity. I also moved the details to the contains() method as that is the one that truly contains the logic in the impl. I referenced contains() from check().

Thanks,
Jim

@codyhoag.