UI: Don't show 'everyone' group for query access (#59)

* Query access for 'everyone' does not work, but trust level 0 does,
and it works the same

assets/javascripts/discourse/controllers/admin-plugins-explorer.js.es6

@@ -67,8 +67,8 @@ export default Ember.Controller.extend({
 
   @computed("groups")
   groupOptions(groups) {
-    return groups.map((g) => {
+    return groups.filter(g => g.id !== 0).map(g => {
-      return { id: g.id, name: g.name };
+      return { id: g.id.toString(), name: g.name };
     });
   },