[ticket/12620] Allow the user to define multiples environments

PHPBB3-12620
[ticket/12620] Fix tests

PHPBB3-12620
[ticket/12620] Display error message when the environment isn't available

PHPBB3-12620
[ticket/12620] Rename debug to development

PHPBB3-12620
[ticket/12620] Improve error message

PHPBB3-12620
[ticket/12620] Fix functional tests

PHPBB3-12620
[ticket/12620] Rename productive to production

PHPBB3-12620
[ticket/12620] Fix functional tests

PHPBB3-12620
[ticket/12620] Split the environments into differents folders

PHPBB3-12620
[ticket/12620] Add inheritance between environments

PHPBB3-12620
[ticket/12620] Rebased to the latest develop-ascraeus

PHPBB3-12620
[ticket/12620] Update tests

PHPBB3-12620
[ticket/12620] Rebased on develop

PHPBB3-12620
[ticket/12620] Use PHPBB_ENVIRONMENT

PHPBB3-12620
[ticket/12620] Move the routing file to the environments

PHPBB3-12620
[ticket/12620] Add the support of the environments for the ext services

We look for an environment.yml file in the config/PHPBB_ENVIRONMENT/
directory of the extensionss. If the directory does not exist we look
for the environment.yml file in the 'default' environment and finally
for the services.yml file in the config/ directory.

PHPBB3-12620
[ticket/12620] Fix tests

PHPBB3-12620
[ticket/12620] Add support of the environments for the ext routing files

PHPBB3-12620
[ticket/12620] Fix download/file.php and app.php outside of the root_path

PHPBB3-12620
[ticket/12620] Uses a cache directory per environment

PHPBB3-12620