[enhancement] Google Authentication setup

[Marcos-A]

• Google Authentication setup instructions should be accessible from outside the installation process.
• Installation process should be able to be interrupted and resumed to set up the Google Authentication process.
• When adding the "Authorized JavaScript origins → Add URI:" parameter, adding "http://127.0.0.1:8000" will work and probably will be more versatile.
• When adding the "Authorized redirect URIs → Add URI:" parameter, in case the app is being installed in a container, showing the container IP as a value (e.g. "http://10.42.28.136:8000/google/login/callback") is misleading, since it's an internal IP. Redirections should be taking into account and a warning should be displayed in that case.

[FherStk]

• The tutorial will be exported into a file called 'how-to-google-developers-console.txt'.
• The process can be interrupted, and the installer will resume it.
• 127.0.0.1 origin works only for local installations, but fails for LXD containers or similar, so the selected approach is to use the 'teaching-stats.com' fake domain, always.
• The same as the previous one for redirections.