PSR-11: Container interface

[bulton-fr]

https://www.php-fig.org/psr/psr-11/

Use that to have a system which can be in the idea of symfony services. But all system added to the container are not auto instancied and not auto-added.
For all system, it's the module which instancied the system/service and add it to the container.

Also, all property currently acceded by Application::__get() will be moved to the container, and Application::__get() will call Container::get().