Table of contents revealed via swipe instead of drag.

For now performance was too poor on iOS 6 to redraw
continuously during drag event.

There's still an unacceptably long delay on 3gs on
large articles between the time the table of contents
is tapped and the time it is initialized. More
updates in near future for this.

TOC drag disabled if there's no article loaded yet.

Pull to refresh disabled if there's no article loaded.

History, saved pages, search results and language picker
no longer use blue table cell selection color on iOS 6.

Change-Id: I67175f141902193c1290cc1307dabb5d14152c74