Jet hypo - provide an optimisation for JetGroupProduct
First optimisation: JetGroupProduct is a widget that finds combinations of jet indices where each entry is drawn from the list of jet indices that satisfy a Condition. The combinations formed by the widget contain no duplicate indices.
For example, for the simple case with 2 Conditions, if Condition 1 Is passed by jets (1, 2, 3), and Condition 2 is passed by jets (1, 2, 4), then JetGroupProduct calculates the combinations as (1, 2), (1, 4) (2, 1), (2, 4), (3, 1), (3, 2), (3,4). Until now, JetGroupProduct internally calculated all combinations - ie the above plus (1,1), (2,2), and then removed the sequences with the duplicate entries.
Second optimisation: Do not return a jet index sequence from JetGroupProduct if it differs only in the order of the het indices from a sequence that has already been returned.
Contains code changes for NR !40641 (closed)