Fixed multi bar graph width for data diff size

When multi-bar graph is used, the width between arrays can change.
e.g.: if you have 6 values for 2007, 6 values for 2008, but only 3 values for 2009, the previous code would apply the width of 2009 bars to the 2008 and 2007 bars.
This adds the width to the different bars generated and only does positioning for multi.