[doc] Introduce Doxygen generation of docs.

  * Add CMake updates to handle Doxygen and Graphviz.
  * Add Doxygen template file.
  * Made the base Doxygen configuration a bit tighter.
  * Update Doxygen configuration.
  * Add layout for documentation site.
  * Update documentation config and CMake.
  * Updated ignores, Doxygen templates and doc generation.
  * Bumped up Doxygen file.
  * Bumped CMake changes.
  * Update document generation for Wintermute.