title: amChart chartScrollbar does not work on mobile devices
body: <p>I have web app which runs on mobile devices and uses amChart. The chart itself is working fine but the chartScrollbar doesn't react on touch events. Both sliders can't be move so it's not possible to zoom into the chart.</p>
  
  <p>This is my code:</p>
  
  <pre><code>            var chartData = this._getData();
  
              var chart = new AmCharts.AmSerialChart();
              chart.categoryField = "date";
              chart.dataProvider = chartData;
              chart.dataDateFormat = "YYYY-MM-DD";
              chart.pathToImages = qx.util.ResourceManager.getInstance().toUri("resource/app/external libraries/");
              chart.valueAxes.title = "Nm³";
              chart.addTitle("Configured Chart 1",14,"#000000",false);
  
              var graphLine = new AmCharts.AmGraph();
              graphLine.valueField = "value";
              graphLine.type = "line";
              graphLine.title = "Ausstoß Biogas";
              graphLine.bullet = "round";
              graphLine.bulletBorderAlpha =  1;
              graphLine.bulletColor =  "#FFFFFF";
              graphLine.bulletSize = 5;
              graphLine.hideBulletsCount = 50;
              graphLine.lineThickness = 2;
              graphLine.useLineColorForBulletBorder = true;
  
              chart.addGraph(graphLine);
  
              var categoryAxis = new AmCharts.CategoryAxis();
              categoryAxis.parseDates = true;
              categoryAxis.dashLength = 1;
              categoryAxis.minorGridEnabled = true;
  
              var valueAxis = new AmCharts.ValueAxis();
              valueAxis.title ="Nm³";
              chart.addValueAxis(valueAxis);
  
              var chartScrollbar = new AmCharts.ChartScrollbar();
              chartScrollbar.autoGridCount = true;
              chartScrollbar.graph = graphLine;
              chartScrollbar.scrollbarHeight = 40;
              chart.chartScrollbar = chartScrollbar;
  
              var legend = new AmCharts.AmLegend();
              legend.useGraphSettings = true;
              legend.align = "center";
              chart.addLegend(legend);
  
              chart.categoryAxis = categoryAxis;
  
              chart.zoomToIndexes(chart.dataProvider.length - 40, chart.dataProvider.length - 1);
  
              this.addListenerOnce("appear", function() {
                  chart.write(this.getChildControl("comp").getContentElement().getDomElement());
                  this.addListener("resize", function(){
                      chart.invalidateSize()
                  });
              }, this);
  </code></pre>
  
  <p>Is there a way to fix this? Or is there a different way to use the amChart zooming functionality on mobile devices?</p>