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](https://github.com/Incenteev/ParameterHandler) that helps migrating configuration (in case we decide to add or rename a param) or creating the file for the first time and can remove 2 steps from the installation guide (since he doesn't need to edit the config and we can create the database ourselves)

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.