[RFC/WIP] Refactoring basic CMS tutorial into book

| Q             | A
| ------------- | ---
| Doc fix?      | no
| New docs?     | no
| Applies to    | all (or 2.3+)
| Fixed tickets |

The idea here is to provide a complete guide to creating a functional CMS, in addition to the existing "Create a CMS using Routing Auto" refactored into chapters here, I would like to add:

- Chapter on integrating the BlockBundle
- Chapter on integrating the MediaBundle
- Other stuff.

What do you think? I figured the monolithic article wouldn't scale very well ...