leaflet-client: Add metic support

Add metric support

merged commits github.com/calendar42/OpenTripPlanner/: 
* 8165908a3e2e8050948871abce69dcd255db7730
* f703f083c9d5d58c05fc739324b9552a8617714a
* 2628e222e1651dbf219964f647740d96458b5dd6
* b5c4cb18173d537762c7c7829c71d10abc289a9c
* 464d7c80252e2c26e3c797d7eab401f9e157281b
* b4846355c6a80441af8fa77c438fab1a36303d7e