Commit cf853a78 removed all yml tests
and the yml import engine from Odoo forever, however PyYAML remains a
dependency even though it's not used anymore.

This commit removes any reference to this lib that could be found.

closes odoo/odoo#27563

Sometime, we need to get selection values from
a method. Here are the guidelines about how
to correctly name method and place it in the
code.

Odoo evolves and its coding guidelines too.
This commit :
 - put some news guidelines, case to take
 into account when making new dev
 - update some guidelines that are difficult
 to applied in the real life
 - remove deprecated stuff (RML report, ...)
 - remove references to old
 api mainly, since all new dev must be done in
 new api

Task #1817988

The same content is already there 2 lines above.

cherry-pick of 57676dc7

The same content is already there 2 lines above.

The state of the JS documentation was quite sad, not updated in a long
time.  With this commit, we rework a lot of the JS doc.  Most notably,
we add a section 'Javascript Cheatsheet' (help on some common
customization tasks) and rewrite the 'Javascript Reference' totally.

Note that the JS reference page also contains a reference on all field
widgets.

This work is just the beginning, it is probably not complete, but at
least we will have a foundation.

The state of the JS documentation was quite sad, not updated in a long
time.  With this commit, we rework a lot of the JS doc.  Most notably,
we add a section 'Javascript Cheatsheet' (help on some common
customization tasks) and rewrite the 'Javascript Reference' totally.

Note that the JS reference page also contains a reference on all field
widgets.

This work is just the beginning, it is probably not complete, but at
least we will have a foundation.

Github will automatically close the report is you use the format
Closes #number
No need to a leading #
cf https://help.github.com/articles/closing-issues-using-keywords/

Add the meaning of [I18N] tag

This commit is an example of a violation of the "one commit, one fix" principle

Purpose of this commit is to clean a bit the wording and to clarify how to
handle guidelines between stable and development versions.

Purpose of this commit is to explain with more details how to write commit
messages. Content of the Git section is also updated with last decisions
and conventions.

There is only one API, long live Odoo's API!

Closes #20928

Some bits posterior or leftover from fffaf735

See also parent commit.

Because now is no longer required

Closes #18144

Typo
Closes #14652

- As of v10, manifest files should be named `__manifest__.py`
- For backwards-compatibility, __openerp__.py manifest files
  will still be supported for the time being
- Limited refactoring, to add support for the 2 different
  naming conventions
- All textual references to __openerp_.py updated in
  documentation and examples

This attribute has been removed from the web framework since b4c28050
and should not keep example of code with it.
Related to #5987

- add python idioms
- odoo specific guidelines (for ORM, translations, ...) inspired from old guidelines v6.0
- some other best pratices

- correct typos
- clarify some points, according to the community comments
- precise the xml notation : record tag vs act_window/menuitem/... tags
- add organization of report, wizard, data/demo, ... (directories and naming conventions)
- new conventions for 'symbols'
- ...

Thanks to @rim-odoo for its grammar extremist review, and @tde-banana-odoo for our long debates about wizard conventions.

To prevent huge chunk of modifications for styling reasons (e.g. mass PEP8
commits)

According to PEP-263, the -*- is just a variant "using formats recognized by
popular editors".

Can still be mentionned in documentation but should not be used in example.

Some rephrasing to slightly improve the docs.
Closes #11652

Backport of most of #6827 by J Bradshaw with additional
modifications (and some reverts) during review.

closes #6827

Pretty much completely rewritten theme with custom HTML translator and a
few parts of the old theme extracted to their own extensions.

Banner images thought not to be that huge after all, and not worth the
hassle of them living in a different repository.

co-authored with @stefanorigano

[ADD] doc : odoo official coding guidelines. This is the first version of the guidelines. Discussions and conventions are not frozen.