amenity=bench: Add armrest field, move color to moreFields (#1227)

data/fields/armrest.json

@@ -0,0 +1,12 @@
+{
+    "key": "armrest",
+    "type": "check",
+    "label": "Armrests",
+    "strings": {
+        "options": {
+            "undefined": "Unknown",
+            "yes": "One or more armrests",
+            "no": "No armrests"
+        }
+    }
+}