In odoo/documentation-user#945, the developer documentation is merged
with the user documentation in a single repository and build config.

This commit then removes source files for the developer documentation
from the odoo/odoo repository.

DOC PR: https://github.com/odoo/documentation-user/pull/945

task-2351938
task-2352371
task-2205684
task-2352544

Co-authored-by: Victor Feyens <vfe@odoo.com>
Co-authored-by: Antoine Vandevenne <anv@odoo.com>

Before this commit, links to the documentation were referenced the
previous version, 13.0, instead of the current one, 14.0.

Eventhough there is a redirection done by NGINX of a "versionless" URL
to the latest one (e.g. /documentation/user/general/auth/google.html
-> /documentation/user/14.0/general/auth/google.html as of today), the
goal is to keep links owrking for users that will still be using the
14.0 in three years (and should not endup on the 17.0 doc).

closes odoo/odoo#59554

Signed-off-by: Martin Trigaux (mat) <mat@odoo.com>

Was still pointing to old links

closes odoo/odoo#37859

Signed-off-by: Adrian Torres (adt) <adt@odoo.com>

Was pointing to a file that no longer exists

Fixes odoo/odoo#27741

closes odoo/odoo#27755

Because now is no longer required

Closes #18144

- 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

NB : Some tests have been modified.
One assert statement in orderpoint_calendar.yml has been modified,
but the change is legit has no python method has been modified at all