Add optional donation code to a donation page

optional_designation_code.html

<fieldset>
<legend>Designation Code</legend>
<p>This is an area where you can make a pitch.  It can run on for as long as you want, or not exist at all.</p>
<div class="formRow">
  <label for="designation_code">Organization</label>
  <input type="text" id="designation_code" name="Designation_Code" val="">
</div>
</fieldset>