Add basic tag position to fire_hydrant (#418)

As per osm wiki, emergency=fire_hydrant should have the
fire_hydrant:position tag.
https://wiki.openstreetmap.org/wiki/Tag:emergency%3Dfire_hydrant

data/presets/emergency/fire_hydrant.json

@@ -10,6 +10,7 @@
     "moreFields": [
         "fire_hydrant/diameter",
         "fire_hydrant/pressure",
+        "fire_hydrant/position",
         "level",
         "survey/date",
         "water_volume"