Fancier config

(WORK IN PROGRESS - Do not merge)

This makes the configuration file [a .yml file that looks nicer](https://github.com/kongr45gpen/bzion/blob/yaml-config/app/Resource/config.yml) and is more user friendly. There's also a package that helps migrating configuration (in case we decide to add or rename a param) or creating the file for the first time.

On the other hand, you'll either have to trust that nothing goes wrong with `.htaccess` (because yml is plaintext and the webserver will show it to the user by default) or move `index.php` to a separate `web` folder and have the user create a symlink there.