Build iD.Way.areaKeys from presets

This eliminates the possibility that a feature will
flip from area to line when you apply a preset.

Fixes #1996

data/presets/presets.json

@@ -1484,8 +1484,7 @@
     "boundary/administrative": {
         "name": "Administrative Boundary",
         "geometry": [
-            "line",
-            "area"
+            "line"
         ],
         "tags": {
             "boundary": "administrative"

data/presets/presets/boundary/administrative.json

@@ -1,8 +1,7 @@
 {
     "name": "Administrative Boundary",
     "geometry": [
-        "line",
-        "area"
+        "line"
     ],
     "tags": {
         "boundary": "administrative"