improve class=path styling (#1450)

This PR addresses that by:

* rendering oneway arrows on more than `subclass=cycleway`
* less opacity for path/footway casing
* adding the thin black casing to bridges
* adding `subclass=steps` & `subclass=bridleway` rendering
* render `bicycle=designated` as `subclass=cycleway` and `horse=designated` as `subclass=bridleway` (bike taking priority)
* improved tunnel rendering with double casing & adding main line
* made casing min zoom consistent across subclasses

All of these changes were made to mimic OSM Carto.

layers/waterway/style.json

@@ -282,7 +282,7 @@
           "bridge"
         ]
       ],
-      "order": 103
+      "order": 111
     },
     {
       "id": "waterway-bridge",
@@ -322,7 +322,7 @@
           "bridge"
         ]
       ],
-      "order": 104
+      "order": 112
     },
     {
       "id": "water_way_name",
@@ -367,7 +367,7 @@
           "LineString"
         ]
       ],
-      "order": 142
+      "order": 151
     }
   ]
 }