Table of contents with section images!

Presently TOC is invoked with a 2 finger tap - will probably change.

Fixed section div numbering bug.

Fixed "Loading remaining sections" message bug.

Can now track with precision html element locations both in web view space
and screen space. Even accounts for pinch zoom level!

Style fixes for overflow tables narrower than their parent elements.

Hide audio tags for now.

Change-Id: I480e36d53a36b1f8506e22e1f887f78cb7fd0a19