add support for cycleway=separate (#540)

https://wiki.openstreetmap.org/wiki/Tag:cycleway%3Dseparate

data/fields/cycleway.json

@@ -43,6 +43,10 @@
             "opposite": {
                 "title": "Contraflow bike lane",
                 "description": "A bike lane that travels in both directions on a one-way street"
+            },
+            "separate": {
+                "title": "Cycleway mapped separately",
+                "description": "Indicates that cycleway was mapped as a separate geometry"
             }
         }
     }