[IMP] core: make author field mandatory in manifests

External contributors (and namely Odoo PS) forget to set the author
field in their manifest file. The result is that the module is wrongly
registered with `'author': 'Odoo S.A.'`.

This work makes the field mandatory, with a warning when not set. It
also offers an upgrade-code script to mass-rewrite all the manifests in
order to set the author.

task-4485983

Author: Julien00859

content/developer/howtos/accounting_localization.rst

@@ -277,6 +277,7 @@ Basic :file:`__manifest__.py` file for such a module looks as following:
         "name": "COUNTRY - Accounting Reports",
         "category": "Accounting/Localizations/Reporting",
         "version": "1.0.0",
+        "author": "Odoo S.A.",
         "license": "OEEL-1",
         "depends": [
             "l10n_XX", "account_reports"

content/developer/tutorials/server_framework_101/02_newapp.rst

@@ -63,7 +63,7 @@ On the other hand, the ``__manifest__.py`` file must describe our module and can
 Its only required field is the ``name``, but it usually contains much more information.
 
 Take a look at the
-`CRM file <https://github.com/odoo/odoo/blob/fc92728fb2aa306bf0e01a7f9ae1cfa3c1df0e10/addons/crm/__manifest__.py#L1-L67>`__
+`CRM file <https://github.com/odoo/odoo/blob/master/addons/crm/__manifest__.py#L1-L67>`__
 as an example. In addition to providing the description of the module (``name``, ``category``,
 ``summary``, ``website``...), it lists its dependencies (``depends``). A dependency means that the
 Odoo framework will ensure that these modules are installed before our module is installed. Moreover, if