[doc] Add more documentation tools and content.

  * Add Code of Conduct for the Wintermute project.
  * 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.
  * Updat ignores, Doxygen templates and doc generation.
  * Update document generation for Wintermute.
  * Fix issue with mainpage being included.
  * Allow extra files to be loaded in for README purposes.
  * Add version file, move docs into silo.