Integrate Leaflet.AutoLayers?

[krlmlr]

https://github.com/aebadirad/Leaflet.AutoLayers

This plugin supports other map service types, so perhaps it should live in {leaflet} or another package?

The simple example works, with a limitation: initially only five or six layers are shown, adding a layer and then removing it from the "Selected overlays order" menu makes the full list visible.