spine plots in BarChart class

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I'd like to be able to add a second data array to BarCharts to produce spine 
plots. setData(float[] values, float[] values).
This would mean that we could use produce spine plots with highlights by 
overlapping BarCharts that contained different data in the first array (length) 
but the same data in the second array (width).  

Original issue reported on code.google.com by jsnd...@gmail.com on 24 Aug 2010 at 8:01