Fix ParameterNotFound Exception

If no data hydrators are defined, i get a ParameterNotFound Exception.

```
  [Symfony\Component\DependencyInjection\Exception\ParameterNotFoundException]
  You have requested a non-existent parameter "spy_timeline.filter.data_hydrator.locators_config". Did you mean this: "spy_timeline.filter.data_hydrator.class"?

```
perhaps rather than doing this we should set default configuration on the Configuration.php or extension classes