texture loading in background

Strangely, it appears as if WebGL in Chromium is queuing up texture creation and doing that in a big batch that blocks the browser, only unblocking when all texture creations complete.

But not in Minefield, which seems to create the textures immediately, where you get slow scene interactivity in the meantime.

I found that even if I substitute untextured geometry to render in place while texture loads, it has no effect in Chromium because it seems the whole browser is being blocked for all the texture loads.

Eventually I plan to use worker threads I think.

So the COLLADA parsing is actually very fast - I'll show that with logging of texture loads and an example showing no textures.

Confirmed: geometry is initially rendered without textures in their absence, but then WebGL texture creation happens in a big burst and freezes everything.

Will detect support for Web workers and employ those in supported browsers.