Add new demo for transforms, make code work locally.

New Unit 7 demo for the viewing pipeline. Also, set the path to "" for
much of the code so that these programs work locally on machines. Note
inclusion of sprintf for new demo.
Make demo more standalone

Dependency on a headerElement existing is removed.
Render scene to near frustum

The view of the scene is texture mapped onto the near plane.
Fix help file to match program
Fix offset for floating billboards
Better view volume visualization

Add perspective view and depth cueing (doesn't work in orthographic) for
volume, add planes for depth levels.
Make coordinate axes more visible

Make them large enough to be clearly seen in smaller viewport.
Fix text maximum scale

A tiny fidget: make the maximum text scale such that it does not extend
off the page.
Better starting camera for Magnification

The student might not realize that the view can be moved. It's better to
start with a view that gives some jaggies at the start.
Make camera view match

Make the demo's view match the texture in the lesson that follows
Faster update of viewport

Instead of recreating the viewport every frame, selectively update it as
needed. Less jerky interaction
One more tweak

Make opacity vary for the depth layers, to help aid perception.
Merge pull request #32 from erich666/master

Add new demo for transforms, make code work locally.