Qwt TODO list

Ideas
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- Improve Documention
- QAbstractModel -> QwtSeriesData
- Curves for financial charts, box-whisker
- QwtSeriesData + functors
- QwtSeriesData/QwtPlotCurve + Level of details (Douglas Peucker)
- Common zoom stack for all navigation objects
- Watermark Item
- Contour algorithm for vectors: http://apptree.net/conrec.htm
- OpenGL plot canvas
- Time/Date scale engine
- TeX texts
- Grid of QwtPlots
- Interval scale labels ( between 2 ticks )
- More than 4 axes
- QwtPlotLegendItem: legend item on the canvas
- QwtSymbol/QwtIntervalSymbol + QPainterPath
- QwtPlotScene + breaking composite architecture
- Using QStaticText for markers ( and scales ? )
- Using QAbstractSlider as baseclass of QwtAbstractSlider

Bugs/Change requests
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1) QwtPlotDict, performance of z sorting
2) Layout init of round scales too late.
3) Remove QwtScaleTransformation::copy()
4) Remove valid flag of QwtScaleDiv
5) Reference value for QwtThermo
6) Transparent canvas background + backingstore
7) Conflicts of qtAddLibrary with installed versions
