title: Parameter "f" in GET api/issues/search
body: <p>I am trying to use the Web Service API - specifically the parameter <code>f</code> for the API <code>GET api/issues/search</code>. </p>
  
  <p>The documentation says that I can use this to specify the fields to return.  </p>
  
  <p>But I can't get it to work. I keep getting the error response below. Is this parameter not yet supported?  My Sonarqube deployment is version 5.0.1.</p>
  
  <blockquote>
    <p><code>{"errors":[{"msg":"Value of parameter 'f' (KEY) must be one of: []"}]}</code></p>
  </blockquote>
  
  <p>Here is my request:</p>
  
  
  
  <pre><code>{
      url: sonarHostUrl + "/api/issues/search",
      type: "GET",
      data:
      {
          assigned: "true",
          componentRoots: projectKey,
          statuses: "OPEN,CONFIRMED,REOPENED",
          ps: "-1",
          hideRules: "true",
          ignorePaging: "true",
          s: "SEVERITY",
          f: "KEY,SEVERITY,ASSIGNEE"
      }
  }
  </code></pre>