Added a new method to generate parameters.yml automatically

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | https://github.com/symfony/symfony-standard/issues/691
| License       | MIT
| Doc PR        | -

This is the first step into removing the parameter handler when installing Symfony.
This won't be necessary if they accept [this proposal](https://github.com/symfony/symfony-standard/issues/694).