GanttChart should feature Entry colors
Description
Goal:
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The user should have the option to customize a gantt entrys color.
So a GanttEntry implementation should be added which has a color member and features proper color rendering.
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Current situation:
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Only the default EntryRenderer (blue) is used.
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Suggested changes:
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Add a ColorGanttEntry implementation which features the mentioned goals.
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Environment
None
Duplicate
