closes #3336

Implicit relative imports have been removed in Python 3, and developers
should be encouraged to use explicitly relative imports to avoid
confusion between local and global modules

See https://www.python.org/dev/peps/pep-0328 for PEP on the subject with
reasonings and justifications

fixes #4711

* document and warn that checks and fast_suite in tests sub-packages are
  deprecated and have no effect
* avoid iterating all currently loaded modules when looking for test
  modules in a tests sub-package
* replace use of __import__ by importlib

Fixes #3152

mostly to match apparent searches for it

Attempt to fix and clarify the guide.

I still can not get "Advanced Customization" to work.

closes ##4291

remove psutil dependency under windows

reverts documentation commit 96aba067 because
it prevent sphinx build

merge setup source code and vcs checkout sections and simplify wording

simplify source installation instructions for windows

Courtesy of: Michiels Denis

Closes: #4249

Courtesy of Moises Lopez

Closes: #4336

add new requirements to generate the docs.

* Odoo installation from packages or source
* Deployment instructions for production environments
* dbfilter

Add missing support for disabling xmlrpc(/http), useful for WSGI
deployments which require running cron-only Odoo instances.

fixes #3157

closes #2623

* The dashboard from the backend howto doesn't specify "name" field
  which causes non-null constraint violation.
* Some useful examples uses idea.idea" model which isn't available in
  8.0 so I replaced them with "note.note".

closes #3993

closes #3594

closes #3874

* use static imports in java examples to make them terser
* inline ``domain`` in java and php example to make examples more
  self-contained
* try to extend/improve Model.write's docstring
* add convenience kwarg to fields_get, mostly for user-driven
  introspection

Closes #3689

closes #3761

When creating a class with the new API, we should use models.Model
instead of just Model.

closes #3713

* add latex support for exercise admonition
* latex freezes/crashes on {HEAVY WIDE-HEADED RIGHTWARDS ARROW} so
  replace them by more manual arrows
* add some preamble configuration, may not even be necessary
* generate WS setup code only in HTML output. WS doc in latex still
  isn't great as it displays all 4 languages one after the other,
  ideally they should be tagged or something, so only one language at a
  time is generated in non-HTML outputs

Doc pages used container() which is width-limited, works acceptably for
single-column content but WS page takes 2 columns with code, having as
much space as possible is a much better idea.

Mayhaps it should even use lg-column(2) instead of md-column(3)?