Extract Renderer code to a single class/interface

[ForNeVeR]

Currently there's a Box.Draw method that's implemented in a relative small number of classes.

For further extensibility, I'd like these methods to be extracted to the IRenderer interface and WpfRenderer class using the Visitor pattern (or something alike).

In future, we'll likely extract Box.RenderGeometry (that has the same form as the Draw method) to another IRenderer implementation, GeometryRenderer. That will also open a way for alternate implementations, such as DirectXRenderer and AvaloniaRenderer.