add fields for level crossing (#194)

data/presets/railway/crossing.json

@@ -1,5 +1,10 @@
 {
     "icon": "temaki-pedestrian",
+    "fields": [
+        "crossing/barrier",
+        "crossing/bell",
+        "crossing/light"
+    ],
     "geometry": [
         "vertex"
     ],

data/presets/railway/level_crossing.json

@@ -1,5 +1,10 @@
 {
     "icon": "maki-cross",
+    "fields": [
+        "crossing/barrier",
+        "crossing/bell",
+        "crossing/light"
+    ],
     "geometry": [
         "vertex"
     ],