Further work on JENA-441
Generalize the optimization to deal with ORDER BY + REDUCED as well as ORDER BY + DISTINCT
Generalize the optimization to allow any sort conditions provided all mentioned variables exist in the projected variables
Add additional test cases to validate

git-svn-id: https://svn.apache.org/repos/asf/jena/trunk@1469989 13f79535-47bb-0310-9956-ffa450edef68