[tox] Have less test environments This is to reduce the load on CI server because of parallel clones of the repository in Docker containers. Only keep "server", and "web" environments separated. All other prior environments are in "misc". To avoid duplicate entries in requirements files, move them all in a "requirements" directory (this appears to be a "common" practice, see e.g. Celery). Adjustments in tests: * Rename cubicweb/hooks/test/unittest_notification.py so that it does not conflict with cubicweb/sobjects/test/unittest_notification.py during test discovery as they would have the same module name but different __file__ attribute. * Add "comment" cube to the list of expected cubes in unittest_cwconfig.py as this cube is pulled by requirements/test-mist.txt. Closes #15440662.

Tutorials
~~~~~~~~~

We present a few tutorials of different levels. The blog building
tutorial introduces one smoothly to the basic concepts.

Then there is a photo gallery construction tutorial which highlights
more advanced concepts such as unit tests, security settings,
migration scripts.

.. toctree::
   :maxdepth: 1

   base/index
   advanced/index
   tools/windmill.rst
   textreports/index
   dataimport/index