Improve page layout - add side panels

Side panels can be used to display content (eg: advertisments) but can be hidden/shown by the user.
They will also resize and disappear if the window isn't big enough.

The middle pannel with the game takes priority. Everything else is resized or removed.
If the window gets smaller than 640x480 there isn't much we can do? Zooming out in the browser should help?

Made information bar and made status bar smaller.

I'm not sure whether I'm allowed to actually put ads in the side panels.
Or whether I want to.

But the panels can be used for other stuff, and I've learned how to use <div> (sort of).
Merge branch 'master' of https://github.com/szmoore/htr-webgl

No idea why merge is necessary.