add access=customers value (#326)

closes #47

data/fields/access.json

@@ -45,6 +45,10 @@
                 "title": "Destination",
                 "description": "Access allowed only to reach a destination"
             },
+            "customers": {
+                "title": "Customers",
+                "description": "Restricted to customers at the destination"
+            },
             "dismount": {
                 "title": "Dismount",
                 "description": "Access allowed but rider must dismount"

interim/source_strings.yaml

@@ -38,6 +38,9 @@ en:
         # access=*, foot=*, motor_vehicle=*, bicycle=*, horse=*
         label: Allowed Access
         options:
+          customers:
+            description: Restricted to customers at the destination
+            title: Customers
           designated:
             description: Access allowed according to signs or specific local laws
             title: Designated