[birt-dev] CheckIn: Refinement of Difference & Area chart renderer

["Yulin Wang" <yulin.wang@xxxxxxxxxxx>]

- Summary:
Refinement of Difference & Area chart renderer

- Bugzilla Bug (s) Resolved:
N/A

- Description:
1. Added Grident/Image Fill support of Difference/Area chart
2. Improved color choosing policy when using palette color as line color
3. Fixed a bug w.r.t the order of positive/negative color of difference chart

- Tests Description: Manual test
- Notes to Build Team: None
- Notes to Developers: None
- Notes to QA: None
- Notes to Documentation: None

- Files Edited:
/org.eclipse.birt.chart.engine.extension/src/org/eclipse/birt/chart/render/Area.java
/org.eclipse.birt.chart.engine.extension/src/org/eclipse/birt/chart/render/Difference.java
/org.eclipse.birt.chart.engine.extension/src/org/eclipse/birt/chart/render/DifferenceRenderer.java

- Files Added:

- Files Deleted