BarSeries

I don't think we need the BarClass any more.  It is only used in the [insight.Utils.highlightSelector function](https://github.com/ScottLogic/insight/blob/master/src/utils/insight.Utils.js#L66), which appears to be redundant because it is only called on [line 305 of Chart.js](https://github.com/ScottLogic/insight/blob/master/src/charts/Chart.js#L303). I tried commenting this out and the filter highlighting still worked on the front page of the website.

I think we should remove insight.Utils.highlightSelector and delete lines 303-308 in Chart.js.