rewrote and improved HTML for TOC

Attention: Template authors need to adjust their CSS!

Original structure:
div.toc >
  div#toc__header.tocheader.toctoggle > span#toc__toggle.toc_close|toc_open > span
  div#toc__inside > ul.toc > li.level1 > div.li > span.li > a.toc

New structure:
div#dw__toc.open|close >
  h3 > strong > span
  ul.toc > li.toc > div.li > a