update leaflet, add test to only add layers if they are not already in map
update leaflet, add test to only add layers if they are not already in map

geopython/demo.pycsw.org,geopython/demo.pycsw.org,murrayk/demo.pycsw.org,murrayk/demo.pycsw.org,murrayk/demo.pycsw.org,geopython/demo.pycsw.org