cubicweb-leaflet #4029900 Allow to change icon url [validation pending]

prioritynormal
typebug
done in0.2.0
load0.200
load left0.000
closed by#42dcb42e6117 [js] Correctly change icon if url is given, closes #4029900
patch[js] Correctly change icon if url is given, closes #4029900 [applied]