Table of contents work-in-progress.

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