add 'modified' class to fields with changed values

data/presets/fields.json

@@ -327,7 +327,7 @@
     },
     "structure": {
         "type": "radio",
-        "options": [
+        "keys": [
             "bridge",
             "tunnel",
             "embankment",

data/presets/fields/structure.json

@@ -1,6 +1,6 @@
 {
     "type": "radio",
-    "options": [
+    "keys": [
         "bridge",
         "tunnel",
         "embankment",

js/id/ui/preset.js

@@ -114,6 +114,14 @@ iD.ui.preset = function(context) {
             }
         });
 
+        formwrap.selectAll('div.preset-field')
+            .classed('modified', function(d) {
+                var original = context.graph().base().entities[entity.id];
+                return _.any(d.keys || [d.key], function(key) {
+                    return original ? tags[key] !== original.tags[key] : tags[key];
+                });
+            });
+
         event.setTags(tags);
         return presets;
     };

js/id/ui/preset/radio.js

@@ -9,7 +9,7 @@ iD.ui.preset.radio = function(field) {
         var buttonwrap = selection.append('div').attr('class','radio-wrap');
 
         buttons = buttonwrap.selectAll('button')
-            .data(field.options)
+            .data(field.keys || field.options)
             .enter()
             .append('button')
                 .text(function(d) { return field.t('options.' + d, { 'default': d }); })