surface, tracktype, smoothness tags in car profile

thanks to @ftrebien for providing an initial PR at https://github.com/Project-OSRM/osrm-backend/pull/955. 

the current PR uses a simpler way to handle multiple tags: it simply picks the slowest speed mandated by the tags present as well as the road type.

actual speeds have been estimated from the photos at the relevant osm wiki pages, but could be discussed.
it could be set to 150, 200 or 250. but can can in fact go very fast on an asphalt surface.