MediaBundle + CreateBundle - enable persistence.phpcr

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | yes
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | https://github.com/symfony-cmf/symfony-cmf-docs/pull/191

To be merged when the configuration changes for the bundle standards for the MediaBundle and the CreateBundle are merged:
- https://github.com/symfony-cmf/MediaBundle/pull/41
- https://github.com/symfony-cmf/CreateBundle/pull/70