Materialize nodes in bindings so no connection to the node table.

git-svn-id: https://svn.apache.org/repos/asf/jena/trunk@1467279 13f79535-47bb-0310-9956-ffa450edef68
Add materialization (copy structure and touch all (var,node) pairs) 

git-svn-id: https://svn.apache.org/repos/asf/jena/trunk@1467281 13f79535-47bb-0310-9956-ffa450edef68