FEATURE: allow for a localized error when a regex fails in site settings

FEATURE: apply string validation to list site settings (so we get regex)

app/assets/javascripts/admin/templates/site_settings/setting_list.hbs

@@ -3,6 +3,7 @@
 </div>
 <div class="setting-value">
   {{list-setting settingValue=value choices=choices settingName=setting}}
+  <div {{bind-attr class=":validation-error validationMessage::hidden"}}><i class='fa fa-times'></i> {{validationMessage}}</div>
   <div class='desc'>{{{unbound description}}}</div>
 </div>
 {{#if dirty}}