TheCubicWebBook #323877 simpler navigation in the book [open]

To ease the navigation while reading the book, We should have the chapter / section / folder hierarchy on the left side. Also, all sections and subsections should be listed in "Table of contents" instead of having some subsections in the section's introducion. For example, in the "Table of contents", we see:

Part II - Development

  * The data model

but we don't see the "data model" subsections

* The data model

  * Data model definition (schema)

  * Workflow definition

  * Data as objects

  * Migration
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