use Röntgen icon for more presets and field-values

presets:
* Diving Platform
* City Limit Sign
* Turning Loop

fields values:
* `design` field of Power Poles and Power Towers/Portals
* `leaf_type`
* `traffic_calming`
* `volcano:type` and `volcano:status`
* `tower:construction`

data/fields/volcano/status.json

@@ -9,6 +9,11 @@
             "extinct": "Extinct"
         }
     },
+    "icons": {
+        "active": "roentgen-stratovolcano___lava",
+        "dormant": "roentgen-stratovolcano___smoke",
+        "extinct": "roentgen-stratovolcano"
+    },
     "autoSuggestions": false,
     "customValues": false
 }

data/fields/volcano/type.json

@@ -9,6 +9,11 @@
             "scoria": "Scoria"
         }
     },
+    "icons": {
+        "stratovolcano": "roentgen-stratovolcano___smoke_2",
+        "shield": "roentgen-shield_volcano___smoke_2",
+        "scoria": "roentgen-volcanic_cone___smoke_2"
+    },
     "autoSuggestions": false,
     "customValues": false
 }