Form editor update

- when a custom field is updated, the matching form field is now also updated
- ability to toggle "is_required" on First name & Last name
- fixed position of validation errors on segment selection, checkbox and radio
- fixed form subscription not working when using custom fields
- fixed sortable in segment selection after list update (add/remove)
- updated position of messages in form subscription

lib/Form/Block/Checkbox.php

@@ -9,10 +9,6 @@ class Checkbox extends Base {
     $field_name = static::getFieldName($block);
     $field_validation = static::getInputValidation($block);
 
-    // TODO: check if it still makes sense
-    // create hidden default value
-    // $html .= '<input type="hidden"name="'.$field_name.'" value="0" '.static::getInputValidation($block).'/>';
-
     $html .= '<p class="mailpoet_paragraph">';
 
     $html .= static::renderLabel($block);
@@ -35,6 +31,8 @@ class Checkbox extends Base {
       $html .= '</label>';
     }
 
+    $html .= '<span class="mailpoet_error_'.$block['id'].'"></span>';
+
     $html .= '</p>';
 
     return $html;