Disabling `exhale` because it is just overloading things right now.

Hidden in this commit are a couple of other items:
* Enable .md documents for CONTRIBUTING.md to avoid same content not on
  docs.beagleboard.org
* Added graphviz to the venv setup, but that doesn't do much as I think
  it was already there

Update License Terms grid

See merge request !68

Bring back ch06 as it has needed details we need to flesh out.

This reverts commit 526e8e6d.

Gateware design overview and version retrieval

See merge request beaglev-fire/docs!1