* move `trait AsU32` from `gcore::vector::misc` to `gcore`
* move blending and gradient to their own modules
* fix unused warnings
* move `Quad`, `Rect` and `BBox` to `gcore::math`
* extract `ReferencePoint` and transform nodes from `transform`
* move color-related code to `mod color`
* fix unused warning in test code
* move blending-related nodes and code to `mod blending_nodes`
* move ClickTarget code to `mod vector::click_target`
Firestar99