Make an exception for block barriers in bicycle and foot profile.

This adds `barrier=block` exceptions to the respective white lists.

In addition this adds tests to check for the exception in bicycle and
foot profiles and makes sure cars are still not able to cross them.

Checked with:

    cucumber --tags @barrier -p verify

References:

- https://github.com/Project-OSRM/osrm-backend/issues/1643
- http://wiki.openstreetmap.org/wiki/Tag:barrier%3Dblock

features/car/barrier.feature

@@ -19,6 +19,7 @@ Feature: Car - Barriers
             | wall           |       |
             | fence          |       |
             | some_tag       |       |
+            | block          |       |
 
     Scenario: Car - Access tag trumphs barriers
         Then routability should be