Custom Message Validation - QuickFIX/J

Support the ability to specify custom validation code in the data dictionary. For example,

<message>
  <validation language="jruby">
    ... scripted code ...
  <validation>

  <field name="Account">
    <validation language="jython">...
      ... scripted validation ...
    </validation>
  </field>

</message>

This should support data dictionary merging so that validation could be layered on top of an existing data dictionary.