fix for #494 (#550)
fix for #494 (#550)

If a way segment contains more than one `surface` tags (e.g.
`surface=*` and `cycleway:surface=*`), the tag best suited for the
current routing type (currently only *cycling* is supported) is
selected.

i.e. if a `cycleway:surface=` tag belongs to the current way segment
it will be used for the analysis exclusively (all other `surface`
tags are skipped from now on).
nrenner/brouter-web,nrenner/brouter-web,nrenner/brouter-web