Add a ResultSetPeekable interface which adds peek() and peekBinding() to the basic ResultSet interface
Add a ResultSetPeeking which is a wrapper around another ResultSet which adds peeking support
Makes ResultSetMem implement ResultSetPeekable
Expand result set tests to cover peeking

git-svn-id: https://svn.apache.org/repos/asf/jena/trunk@1464792 13f79535-47bb-0310-9956-ffa450edef68