title: Implement X-RateLimit-Limit with wso2
body: <p>I need WSO2 to return at every REST API request the following 3 ratelimit headers:</p>
  
  <ul>
  <li>X-RateLimit-Limit: actual application limit</li>
  <li>X-RateLimit-Remaining: remaining requests </li>
  <li>X-RateLimit-Reset: seconds to the moment of reset</li>
  </ul>
  
  <p>Is there a plugin/mediator allowing this?
  Which HTTP headers does WSO2 notify clients the remaining quota metrics?</p>
  
  <p>Thanks@all!</p>