Move all kinds of things around.

* Collapse core-libraries and core-utility libraries. Not even I can
  remember what goes where. One flatter directory will be much saner to
  handle.
* Remove TOC stubs. These were pointless fluff that just make the docs
  more bloated while contributing nothing.
* Expose more information in the top level TOC. Instead of forcing
  people to hunt, try and bubble up some sections many people might be
  interested in.