Fill gap between QPainter and Qt Quick Shapes

Qt Quick Shapes should be usable as a replacement for drawing shapes with QPainter, but there are certain things missing from the API.

This task is intended to be a collection of smaller items for tracking these.

• Texture brush: Qt Quick Shapes supports gradients, but not arbitrary images/items
• Pattern brush: QPainter supports predefined patterns to use as fill
• QGradient::coordinateMode: Not supported
• Cosmetic pens