Light:  remove waring from bad type conversion.
Objects:  Add render type configuration

WIP : A new render_type `render_type::stencil' has been added.
Polygon:  Always attach a material to help uniform drawing.

This will allow to remove the polygon class and only have one scene that
renders objects as the polygon will considered as objects.
Polygon:  Remove class, only handle Object class for rendering primitves
Camera:  Shift/Ctrl used to increase and decrease the camera's speed.