Added handling of removal of particle systems, ribbons, lines, shadow volumes, marching cubes.

Fixed bug with partial mesh removal.

Reapplied cleanup and bugfixes to zz85's latest Text version, made crashes on bad geometry less fatal.

Still doesn't work properly for Gentilis glyps with holes, but at least now you can see something.

Also some glyphs from Optimer are still problematic depending on tessellation ("B" and "f").

Added font weight and style parameters to Text.

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.