title: Highcharts: How to set dataGrouping
body: <p>I have a highstock graph with lots of data in it, I am able to define how the data can be grouped, but Id like the user to specify which data grouping to use and change dynamically between day, week, month etc.</p>
  
  <p>So is it possible to have a button whereby a user can change how the data is grouped, if so how?</p>
  
  <p>There are many undocumentated features, for example currentDataGrouping, but there's nothing to set the data grouping... that I can see any way...</p>
  
  <pre><code>series: [{
                  type: 'column',
                  name: title,
                  data: data,
                  dataGrouping: {
                      units: [['week', [1]], ['month', [1]]]
                  }
          }]
  </code></pre>