ReductionLinkRule adds links back that have already been hidden

[timdine]

The Reduction Link Rule is a great sample that I've used to remove loops (two parallel lines with the same start and end nodes). It worked perfectly except that when I ran it late in my stack of rules added many lines back into the diagram that had been hidden by previous rules. By removing the line:
"schemElement.Displayed = true;"
at approximately line 225 the rule behaved as I would have expected and honored any previously removed lines. The features should only be hidden by the rule, not added back into the diagram. It is just a sample, but that change makes it more useful for me.