Handle HOV designated-only Lanes, resolves #2929

In https://github.com/Project-OSRM/osrm-backend/issues/2711 we made
`hov=designated` routability configurable.

We want to handle designated-only lanes in the same way. Example:

    hov:lanes:forward=designated|designated
    hov:lanes:backward=designated

should have more or less the same effects as

    hov=designated

In contrast

    hov:lanes:forward=designated|no|yes hov:lanes:backward=yes

should not be handled. See

    https://github.com/Project-OSRM/osrm-backend/issues/2711

for explanation wrt. tag semantics with the difference that
backward/forward only set the backward/forward mode to inaccessible.

References:
- http://wiki.openstreetmap.org/wiki/Key:hov#hov:lanes.3D.2A

taginfo.json

@@ -62,6 +62,24 @@
             "object_types": [ "way" ],
             "description": "Roads with hov=designated are ignored by default."
         },
+        {
+            "key": "hov:lanes",
+            "value": "designated",
+            "object_types": [ "way" ],
+            "description": "Roads with hov:lanes all-designated are ignored by default."
+        },
+        {
+            "key": "hov:lanes:forward",
+            "value": "designated",
+            "object_types": [ "way" ],
+            "description": "Roads with hov:lanes:forward all-designated are ignored by default."
+        },
+        {
+            "key": "hov:lanes:backward",
+            "value": "designated",
+            "object_types": [ "way" ],
+            "description": "Roads with hov:lanes:backward all-designated are ignored by default."
+        },
         {
             "key": "toll",
             "value": "yes",