autoPlay and autoStart parameters

These parameters allow running a presentation non-interactively.
'autoStart' controls when the presentation starts, and 'autoPlay'
whether to pause when reaching 'onClick' actions.

They are encoded as GET parameters to avoid interfering with the
anchor part. It's still possible to use <a href="#something">
to navigate within the presentation. One downside of this is that
changing one auto* parameter requires reloading the page.
autoLoop, to play a presentation in an infinite loop

One can now launch a presentation completely non-interactively by calling it with
?autostart&autoloop&autoplay