QskTreeView

[rick-vogel]

Relates to #309

Tree View

• [ ] use existing scene graph node recycling
• [ ] at least one row can be selected
• [ ] alternating row colors
• [ ] specific row color
• [ ] specific cell text

The core change for the styling are these functions:

./src/controls/QskListView.h

virtual QskAspect::Subcontrol rowSubControl( int row ) const noexcept;
virtual QskAspect::Subcontrol cellSubControl( int row, int col ) const noexcept;
virtual QskAspect::Subcontrol textSubControl( int row, int col ) const noexcept;