[doc] Restructure the documentation * Create a new index file * Move the sphinx configuration files do the documentation root * Move book/README to dev/documenting.rst * Move book/mode_plan.py to tools/ * Move book/en/images to images * Move book/en/* to book/ * Move changelogs to changes/* * Adapt the Makefile * Add a title to the javascript api index Related to #4832808

Data model
==========

This chapter describes how you define a schema and how to make it evolves as the time goes.

.. toctree::
   :maxdepth: 1

   definition
   metadata
   baseschema
   define-workflows