Cleanup docs folder

The docs folder is currently a mess. We only have a few files here, but
it's difficult to see what they are and what's still important.

* Remove obsolete documentation when it is redundant with newer
  documentation.
* Rename remaining obsolete documentation to make clear that it is
  outdated.
* Remove PDFs -- having two versions of every file makes everything very
  cluttered and hard to find. If you can't open VSDs, install Visio or
  LibreOffice.
* PNP test results do not belong here.