Fix bug graphMax

Bug fixed : when  a bar from a (Horizontal)stackedBar graph is beyond the graphMax value, the bars are drawn over Title/Scale.
Fix + negative values for stacked graphs

Enable StackedBar and HorizontalStackedBar with negative values;
+ Fix bug for animation in HorizontalBar
fix bug

Fixed bugs :
- legend not correct
- gradientColor when negative values in HorizontalBar
Update ChartNew.js
Merge pull request #153 from FVANCOP/StackedBarCharts

# Enhancements :

* StackedBar and HorizontalStackedBar can now have negative values;
    
# Bugs fixed
*    Hover info remains on graph (issue #19)
*    legend not correct (inverted) for gradient Colors in Bar/Lines chart
*    gradient Color not displayed correctly on HorizontalBar when negative values in the data;
*    animation on HorizontalBar was not correct in some cases;