When installing Symfony, the parameters.yml is now generated automatically

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #691
| License       | MIT
| Doc PR        | -


**WARNING** This change depends on this other change made on SensioDistributionBundle: https://github.com/sensiolabs/SensioDistributionBundle/pull/155