add support for WMS services that do not support SLD WMS GetLegendGraphic
|Reported by:||bartvde||Owned by:|
Currently WMS legends are based on the SLD WMS GetLegendGraphic request, but not all WMS vendors support this, e.g. ESRI does not have support for it.
They may however advertize a LegendURL in the WMS GetCapabilities response.
So I propose to do the following: if the GetLegendGraphic request fails, fall-back to detecting the LegendURL from the WMS GetCapabilities, if that fails as well fall-back to an blank image.