Changes for radar charts + savePng option 

-> Changes for radar charts have been performed : 
    - in previous version lot of space was lost; In this new version, used space is optimized (option graphMaximized introduced for radar charts);
    - startAngle option added;

-> savePgn option added ; when set to true, a right click on the mouse allows to save the graph in Pgn format;

-> startAngle correction for Pie, Doughnut and PolarArea graphs.