Introduce Material

[ivancea]

Original report by Iván Sanz (Bitbucket: ivansanz, GitHub: isc30).

---

Something like:

Material =

struct MaterialProperties {

        float shininess = 10.f;
        vec3 specularColor = vec3(1, 1, 1);

    };

    struct Material {

        Texture* diffuseMap = nullptr;
        Texture* specularMap = nullptr;
        Texture* normalMap = nullptr;
        MaterialProperties materialProperties;

};