AGPUSH-1107 : Refactored Installations retrieval to work with roles

To test :
* Create App and Variant with developer role
* Add some installations
* log out
* log in as admin
* Verify you can see the developer's installations.

@abstractj @matzew @edewit Could you review/merge ? 
since Join/Predicate and others are final, I think others (e.g. Root, Criteria*) can be final too