Add aircraft holding position type field (close #100)

data/fields/holding_position/type.json

@@ -0,0 +1,14 @@
+{
+    "key": "holding_position:type",
+    "type": "combo",
+    "label": "Type",
+    "strings": {
+        "options": {
+            "runway": "Runway",
+            "intermediate": "Taxiway-Taxiway Intersection",
+            "ILS": "Instrument Landing System"
+        }
+    },
+    "autoSuggestions" : false,
+    "customValues" : false
+}

data/presets/aeroway/holding_position.json

@@ -1,7 +1,9 @@
 {
     "icon": "temaki-plane_taxiing",
     "fields": [
-        "ref"
+        "ref",
+        "holding_position/type",
+        "ele_node"
     ],
     "geometry": [
         "vertex"