How to scale a scene to the screen?

[z3dev]

@evanw Thanks for the nice library. I'm working on OpenJSCAD.org and lightgl is center to the project right now.

However, I'd like to add an option to scale the current scene to the screen. In other words, OpenJSCAD.org uses one (1) to mean one(1) millimeter. There are ways to determine the number of pixels per millimeter on the screen. And I'd like to offer an option to "scale 100%", which would scale the scene to the screen.

Any help is much appreciated.