grafx - Extensible Java Graphics Package Code

Adding a stub for sliverContainsSamplePoint() in Donut. There is a large
comment explaining this, but the signature/implementation have not been done
yet.

Adding a comment explaining the barebones method of computing facet normal,
with a reference to Newell's algorithm.

Moving the new functions into VectorUtils where they belong.

In Donut, adding crossProductXY() and vectorXY().

Struggling with the Donut code to draw vertices.

Removing two unnecessary blank lines.

Adding getPointAlias() to RasterDepthGraphics.

In drawPoint(), moving the z value for the sample point, which occurs at
(i+0.5,j+0.5).

Experimenting with the idea of adding a normal to drawPoint(). Not implemented
yet.

Demonstrating how we need to introduce the concept of "normal" when rendering a
point.