+ Added Materials (CheckerBoard, Bitmap, SolidColor)
+ Introduced Super-class AbstractRayObject
+ Added 4x multithreading for Camera ( takePictureSlice() for taking a piece of the picture. )
* Fixed a bug where I mixed up deltax and deltay variables!
* Changed getPointColor() to handle Vector3d's more efficiently.
* changed Sphere.intersects() to not require a Vector3d instantiation; more efficient.
* changed Sphere.getIntersectionPoint() to only instantiate one Point3d object.
+ Added more Color3f constants (RED, GREEN, BLUE, HALF_WHITE)
+ Added Vector3d.dot that takes (x, y, z) parts as double variables, so I can take dot products without a vector instantiation.