title: Showing marker for separate values only in line chart in HIghchart
body: <p>I'm drawing line chart using Highstock and I wonder if it is possible to add marker only to "separated" points (i.e. points without direct neighbours) in series. It is not possible to see these points if markers are disabled.</p>
  
  <p>I mean data likes this:</p>
  
  <pre><code>    series: [{
          data: [29.9, null, 106.4, null, 144.0, 176.0, null, 148.5, 216.4, 194.1, 95.6, 54.4],
      }]
  </code></pre>
  
  <p>If you look at this fiddle: <a href="http://jsfiddle.net/hvCFD/" rel="nofollow">http://jsfiddle.net/hvCFD/</a> you'll see, that values for Jan and Mar are not visible without mouse hover. I don't want to enable markers globally for the whole data series. Is there another solution?</p>