title: Django admin :: I want to keep last selected value on adding another item
body: <p>Context</p>
  
  <ol>
  <li>in django administration site</li>
  <li>I am adding a new item in a model via <em>add</em> button   </li>
  <li>when the form is displayed, I have a <strong>dropDown</strong>  with some options to choose, I choose option B and I fill other fields to complete the form </li>
  <li>I click on button <em>save and add another</em></li>
  </ol>
  
  <p>When the new "add form view" is displayed 
  I want my <strong>dropdown</strong> to set on the last choice (B option) I selected before </p>
  
  <p>What is your suggestion to implement that as simple is possible?</p>
  
  <p>Thank you</p>