fix#1263
We were calling popagateShow at datalayer init, which then
add a listener to "loaded" event, and then do the propagate.
So when the layer is hidden at load, when dragging it in the
datalayers list, it will be loaded (because we need to save it
with its new position) and it will appears as shown whatever
its real status.
uMap lets you create maps with OpenStreetMap layers in a minute and embed them in your site.
Because we think that the more OSM will be used, the more OSM will be improved.
Built on top of Django and Leaflet.