title: isDirtyBox and isDirtyLegend
body: <p>I found in few of the previous posts like in <a href="https://stackoverflow.com/questions/14947484/dynamically-modifying-the-highchart-layout-options">here</a>, making use of the <strong><code>chart.isDirtyBox</code></strong> and <strong><code>chart.isDirtyLegend</code></strong> properties. I could not find them in the highcharts API either. </p>
  
  <p>What actually do they do ? Can anybody out there help me get the documentation for these properties or help me explaining the use of these properties, possibly with examples?</p>