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/boundary/style.json

@@ -61,7 +61,7 @@
           0
         ]
       ],
-      "order": 137
+      "order": 146
     },
     {
       "id": "boundary_2",
@@ -114,7 +114,7 @@
           0
         ]
       ],
-      "order": 138
+      "order": 147
     },
     {
       "id": "boundary_2_disputed",
@@ -171,7 +171,7 @@
           0
         ]
       ],
-      "order": 139
+      "order": 148
     },
     {
       "id": "boundary_2_disputed_maritime",
@@ -228,7 +228,7 @@
           1
         ]
       ],
-      "order": 140
+      "order": 149
     },
     {
       "id": "boundary_2_maritime",
@@ -281,7 +281,7 @@
           1
         ]
       ],
-      "order": 141
+      "order": 150
     }
   ]
 }