Make the DBAL event store table name configurable.

There is now a bundle configuration option under
```
broadway:
    event_sourcing:
        dbal_event_store:
            table_name: my_events
```
Defaults to `events`.

Fixes https://github.com/qandidate-labs/broadway/issues/90
Alternatively, this could be done with a parameter
```php
$container->setParameter(
    'broadway.event_sourcing.dbal_event_store.table_name',
    $config['dbal_event_store']['table_name']
);
```
This parameter could then be used in the service definition, instead of relying on an argument position.