Don't actually use a form element for the preset form

Form elements have default behavior that we don't want,
such as auto-clicking the first button when pressing return
in a text field.

Fixes #1681

css/app.css

@@ -959,7 +959,7 @@ a:hover .icon.out-link   { background-position: -500px -14px;}
     overflow: hidden;
 }
 
-.inspector-preset form.preset-form {
+.inspector-preset .preset-form {
     padding: 10px;
     margin: 0 10px 20px 10px;
     border-radius: 8px;

js/id/ui/preset.js

@@ -72,10 +72,10 @@ iD.ui.preset = function(context) {
         var shown = fields.filter(function(field) { return field.shown(); }),
             notShown = fields.filter(function(field) { return !field.shown(); });
 
-        var $form = selection.selectAll('form')
+        var $form = selection.selectAll('.preset-form')
             .data([0]);
 
-        $form.enter().append('form')
+        $form.enter().append('div')
             .attr('class', 'preset-form inspector-inner fillL3');
 
         var $fields = $form.selectAll('.form-field')