Makes toll=yes way's routability configurable in profiles.

The primary use-case is conditionally filtering ways such as:

https://www.openstreetmap.org/edit#map=18/38.94198/-77.28127

which we are guiding the user onto in the route from DC to IAD:

http://map.project-osrm.org/?z=12&center=38.934443%2C-77.167969&loc=38.902656%2C-77.029095&loc=38.952210%2C-77.453424&hl=en&alt=0

This changeset makes `toll=yes` configurable in the profiles, disabling
them by default. Neither do we support time-based fees nor vehicle
category fees at the moment.

References:
- http://wiki.openstreetmap.org/wiki/Key:toll

profiles/car.lua

@@ -149,6 +149,7 @@ local turn_bias                  = 1.2
 local obey_oneway                = true
 local ignore_areas               = true
 local ignore_hov_ways            = true
+local ignore_toll_ways           = true
 
 local abs = math.abs
 local min = math.min
@@ -240,6 +241,12 @@ function way_function (way, result)
     return
   end
 
+  -- respect user-preference for toll=yes ways
+  local toll = way:get_value_by_key("toll")
+  if ignore_toll_ways and toll and "yes" == toll then
+    return
+  end
+
   -- check if oneway tag is unsupported
   local oneway = way:get_value_by_key("oneway")
   if oneway and "reversible" == oneway then