title: highcharts change exporting option dynamically
body: <p>I have chart option like below:</p>
  
  <pre><code>'chart' : {
      'defaultSeriesType' : 'bar',
      'renderTo' : QIS.WERM.CcySpotValuationContent.LINE_CHART_AREA_ID_
      },
  'title' : {
      'text' : title
      },
  'exporting':{
      'buttons': {
          'contextButton': {      
              'symbol':'url(/fxqis/public/images/excel.gif)',
              'onclick': function() {}
              }
          }
      }
  </code></pre>
  
  <p>but what I want is to use different exporting option dynamically. like following:</p>
  
  <pre><code>if(something){
      'exporting':{
          'buttons': {
              'contextButton': {      
                  'symbol':'url(/fxqis/public/images/excel.gif)',
                  'onclick': function() {}
                  }
          }
      }
  }
  else{
      'exporting':{
          'enabled':false
          }
  }
  </code></pre>
  
  <p>Can I add such if/else condition in the chart option? How can I do that?</p>
  
  <p>Thanks.</p>