Create documentation for message localization

Also define the `translator` param to the related rules in
`AbstractNestedException`.

library/Exceptions/AbstractNestedException.php

@@ -108,6 +108,19 @@ class AbstractNestedException extends ValidationException implements NestedValid
         }
     }
 
+    public function setParam($name, $value)
+    {
+        parent::setParam($name, $value);
+
+        if ('translator' === $name) {
+            foreach ($this->getRelated(true) as $related) {
+                $related->setParam($name, $value);
+            }
+        }
+
+        return $this;
+    }
+
     public function getRelatedByName($name)
     {
         foreach ($this->getIterator(true) as $e) {