add "unknown" as possible value for access fields

data/fields/access.json

@@ -44,6 +44,10 @@
             "permit": {
                 "title": "Permit",
                 "description": "Access allowed only with a valid permit or license"
+            },
+            "unknown": {
+                "title": "Unknown",
+                "description": "Access conditions are unknown or unclear"
             }
         }
     }

data/fields/access_simple.json

@@ -9,6 +9,7 @@
             "permissive": "Permissive",
             "customers": "Customers Only",
             "permit": "By Permit Only",
+            "unknown": "Unknown",
             "no": "None"
         }
     },