first version of a mail interface for the public api - WIP

:construction: WIP

Result of explanation to @pellaeon how the public API works and the mail class doesn't have a public interface.

@pellaeon will work on that \o/ Thanks

Then have a look at the folder and you will see that there is even an file called `mail.php` and I don't want to f***kup the non-autoloader classes. So this one will have a shitty name, but it's just for the purpose of the server container initialization and the autoloader. nothing more. We can change that once we removed the static version of the mail class