Refactored filterLegend to be faster
Refactored filterLegend to be faster

The function will now only remove or add the gray icons when actually
necessary (versus the old default behavior of adding them to the array
whether or not they would be operated on).

codefordenver/denver-sustainability,codefordenver/denver-sustainability,codefordenver/denver-sustainability,codefordenver/denver-sustainability