Added Texture constructor in IlluminationModel

Contains a single function encapsulating the whole pipeline.
Also added mkPhongTexture to combine the stages of the pipeline.
Added portions of texture pipeline to NabRay
Changed Scene transformation map to only Proj4

It'll be easier to invert for Texture objects, and
we weren't using the generality the (Object->Object) definition
provided.
Texture mapping is go

Added special case to transformLitObject to handle appending
transformations to Textures; necessary to obtain correct mapping
to object space.
Applied red and yellow checkerboard texture to floor.
Added normal to result of intersect calculation
Scene4 properly finds the closest intersection
4d lighting with hackish phong

Reflect function naively promoted to 4th dimension.
Shadow ray omitted.
Shading on solid-colored hyperspheres.

Seems something is awry with specular for w != 0.
Probably something that doesn't make sense with how I ported the
reflect function to 4d.
Merge tag 'checkpoint4' into 4d

Texture mapping -- checkerboard on the floor

I need code to copypasta for the 4d textures.
Texture pipelines incorporated

Uses previously implemented Scene4.objColor to determine the
diffuse coefficients of a generic plastic phong model.