title: Add buttons in chart of Highcharts at runtime
body: <p>I need to add some custom buttons (with onclick events), without overwrite the exporting buttons value, 'cause  I wanna include new buttons without lost the custom buttons previously defined in chart (my chart already has custom buttons defined), all this at runtime, in a Highcharts chart using this object:</p>
  
  <blockquote>
    <p>$('container').highcharts()</p>
  </blockquote>
  
  <p>Is this possible?</p>