This necessitated to rework how light properties for a material were
given. A material can have either reflectivity or transparency. This
changes the parsing of materials, using a `LightProperty` structure at
its core.
This is does not implement the true Fresnel equations to take into
account the amount of reflection that an incident goes through when
encountering a transparent object.
This allows for easier testing (notable allowing for comparisons),
better performance (thanks to inlining instead of vtable indirection),
and should ease the deserialization of `Material`, `Shape`, and
`Texture` traits. This should allow `Object` to be deserialized easily.
