Added modular GPU spline rendering

"SplineGeometry" is a DataNode that moves vertices to follow a thick
spline. The control points, surface normal of the line, and the line
thickness are all DataLine inputs.
Added a warning to DataNode automated function
Added updated project files to recognize SplineGeometry
Fixed compile bug in GUISelectionBox
Improved Gradient class.

Uses linear, cubic, or quintic smoothing instead of specifying slopes
like a spline. Also had to update NoiseTest, giving the "NoiseToPixels"
function a much-needed overhaul