The WLeafletMap widget displays a leaflet map.
It implements a Wt wrapper around the Leaflet functionality.
"tile server", like OpenStreetMap's tile server in this example. If you just create a WLeafletMap,
(and give it a size), then you will be presented with an empty map. You can then add tile layers to the
map using addTileLayer().
WLeafletMap is not exhaustive in its support for Leaflet features. It supports a subset
out of the box. One of these features is markers, which come in two flavors: standard leaflet markers
(WLeafletMap::LeafletMarker) and widget markers (WLeafletMap::WidgetMarker).
Using a widget marker, you can place arbitrary widgets on the map. In this case, a WImage with
Leaflet itself is not bundled with Wt. Use the leafletJSURL and leafletCSSURL properties