Configure a step element configuration value via its setter 

| Q                   | A
| ------------------- | ---
| Bug fix?            | No
| New feature?        | No
| BC breaks?          | No
| Tests pass?         | Yes
| Scenarios pass?     | -
| Checkstyle issues?  | No
| Changelog updated?  | No
| Fixed tickets       | -
| Doc PR              | -

Configure a step element configuration value via its setter if it exists

 @BitOne This allows to configure things like https://github.com/akeneo/pim-community-dev/blob/master/src/Pim/Bundle/BaseConnectorBundle/Reader/File/YamlReader.php#L50