[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.
[wip] Patch Doxyfile.in
[wip] doc: Update extra document files inclusion.

  * Fix issue with mainpage being included.
  * Allow extra files to be loaded in for README purposes.
[wip] doc: Add version file, move docs into silo.

  * Add file for handling versions.
  * Move wintermutecore-specific docs into folder.