Add ability to toggle Sub Layers on/off

Idea created by APologruto_MAWC on Apr 7, 2017

    In ArcGIS Online, I have a viewer set up with 1 layer that contains 55 symbolized sublayers. As of now there is not easy way to toggle that group's visibility on/off easily. A "turn on/off" button on the Parent Layer would save me from clicking.