Layers toggled on in Sidebar Instant App

[JenniferBorlick]

In the Sidebar Instant App Layer List Configuration, have newly added layers toggled ON by default. My thought process for this idea is that when people add a layer to a map, they assume it's going to be there when the map is saved. If someone is adding a layer that they know that they DON'T want to show up in the layer list, they will know they need to go turn it off in the configuration.