[views] simplify and fix the TreeView (closes #16055814) Simplify the (internal) TreeView._init_params() method to get rid of the useless 'initial_thru_ajax' argument. The ajax tree view was not working properly when loaded via ajax, for instance from a lazy tab. This was due to the buggy protection against double javascript/ css inclusion, which is no more needed server-side as it is now implemented client-side. Deprecate use of the initial_thru_ajax argument of the TreeView.call() method.

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