A function to return a url for a leaflet template for use as map backgrounds with the spplot1 function.
urlTemplate(name = "Stamen_Toner")name of the template to use, the default is 'Stamen_Toner'
url for the leaflet template
Possible templates are: OpenStreetMap_Mapnik, OpenStreetMap_BlackAndWhite, OpenStreetMap_DE, OpenStreetMap_France, OpenStreetMap_HOT, OpenTopoMap, Thunderforest_OpenCycleMap, Thunderforest_Transport, Thunderforest_Landscape, Thunderforest_Outdoors, OpenMapSurfer_Roads, OpenMapSurfer_Grayscale, Hydda_Full, Hydda_Base, MapQuestOpen_OSM, Stamen_Toner, Stamen_TonerBackground, Stamen_TonerLite, Stamen_Watercolor, Stamen_Terrain, Stamen_TerrainBackground, Stamen_TopOSMRelief, Esri_WorldStreetMap, Esri_WorldTopoMap, Esri_WorldImagery, Esri_WorldTerrain, Esri_WorldShadedRelief, Esri_WorldPhysical, Esri_OceanBasemap, Esri_NatGeoWorldMap, Esri_WorldGrayCanvas, Acetate_all, Acetate_terrain, HERE_satelliteDay, HERE_hybridDayMobile, HERE_hybridDay
See http://leaflet-extras.github.io/leaflet-providers/preview/ for other leaflet templates