Build 3.5.0.64 of xlsgen adds native rendering of error bars in charts.

Error bar in charts were already supported in the old chart rendering (based on Microsoft OWC) because all xlsgen had to do was to ask them to be rendered. But the new 3.5 chart rendering engine does not depend on any third-party chart engine, therefore this had to be explicitely implemented.


Rendering chart error bars in xlsgen

Error bars details include all the usual suspects :
- X error bars (whenever applicable) and Y error bars
- line formatting
- fixed value, percentage, standard deviation, standard error