Fixes on documentation.

* added redirect_home which is a http refresh redirect. It works like a 301 for google
* replaced previously removed concepts/containers and concepts/introcution by a redirect
* moved orphan index/varable into workingwiththerepository
* added favicon to the layout.html
* fixed an issue in the layout that would make it break when on small screens
* added link rel="canonical" so the pages should not show up at the docker dot readthedocs.org domain.