I think setViewOffset is mostly useful for multiple monitors
synced across multiple machines but that's a hard demo to setup
so these demos show doing it locally with muliple canvases

Examples in another commit

Having these "undefined" for non-mesh objects was causing unnecessary GL state setting when having scenes with mixed content (and coercing "undefined" to boolean turned out to be similarly costly as state setting).

Now it's possible to have antialiased stereo.

Applied latest Vector* improvements to current revision. Ok, that's the last one I promise :P

reworked Vector classes, no change in API, reordered methods, divide-by-zero prevention, removed use of .set() in methods for better performance

Because the gl.finish and the computeCentroids not being enable I though the r41 should include these fixes too, hope this doesn't mess up things.

Added offset and repeat properties to Texture. It'll be tricky to add support for this on CanvasRenderer but should be easy on WebGLRenderer.

It seems lineWidth defaults are different in Chrome and Firefox.

Still there are some clearing artefacts in Firefox :/

Disabled ambient light in trackball Earth example (to get rid of clouds in unlit part of the globe).