title: Null values update with Spring Rest Resource
body: <p>There is a class annotated with RestResource (Spring 3.1, Jackson 2.3). 
  When we try save object A like that</p>
  
  <pre><code>A: {"prop1":1, "prop2":2} 
  </code></pre>
  
  <p>it saved successfully.</p>
  
  <p>We have following code:</p>
  
  <pre><code>A.setProp2(null);
  EntityService.patch(A);
  A: {"prop1":1, "prop2":null} 
  </code></pre>
  
  <p>After EntityService.patch(A) execution there is no changes in DB (Oracle 11g), but we want that in DB prop2 will be equals to null too.</p>
  
  <p>Is it a normal behaviour (I think maybe yes, because null-value may understanding like not changed)? 
  Is there a simple way to change this behaviour?</p>