add Leaflet map service (tested, stable)

* correct auto zoom and position compared with googlemaps
* Displaying a single point {{#display_map:Moscow, Russia}}
* Displaying multiple points {{#display_map:Moscow, Russia; New York; Brussels}}
* Resizable {{#display_map:Moscow, Russia|resizable=yes}}
* max/min -zoom {{#display_map:new york city~New York City|minzoom=4|maxzoom=8|zoom=6}}
* custom icon {{#display_map:Moscow, Russia;|icon=Green_marker.png}}
* lines {{#display_map:Berlin|lines=53.225768435790194,23.466796875:53.9560855309879,29.1796875}}
* polygons (not tested, because the problem in the main code)
* circles (not tested, because the problem in the main code)
* rectangles (not tested, because the problem in the main code)

Change-Id: If4be7cd0d626d8c6642696d0fa5e46351b81771c
Merge "add Leaflet map service (tested, stable)"