removed useless constants.
minor code tweak.
added built-in furry ball curves object.
code cleanups and simplifications.
added link to reference paper.
improved comments.
renamed a method.
minor code tweaks and simplifications.
small code tweak.
small code tweak.
small code tweaks.
fixed side determination for curves.
fixed compilation with Visual Studio 2012.
many code tweaks, fixes, cleanups and simplifications around the curve rendering code.
Bezier curve bounding boxes no longer take the curve width into account.
fixed computation of back point on curves.
honor probe ray length in curve tree probe visitor.
fixed wording.
renamed unit tests and output images.
added unit test.