Add new markers to Leaflet layer group that is then added to map.
Add new markers to Leaflet layer group that is then added to map.

This way all the markers can be removed from the map by clearing
one single layer group.

vaaralav/servicemap,City-of-Helsinki/servicemap,City-of-Helsinki/servicemap,Zeukkari/servicemap,vaaralav/servicemap,City-of-Helsinki/servicemap,vaaralav/servicemap,Zeukkari/servicemap