Fixed lighting in shader, fixed cube texturing

Fixed a couple oversights in the shader.

The first being that the model matrix didn't affect lighting properly.

The second being that I was multiplying each lighting result by their
texture counterparts twice, increasing contrast but in general making
everything darker.

The third change was that I removed material properties. At present
they're fairly redundant.

Oh, and I also changed the texturing on the cube primitive to be more
consistent.