Fixed issue with dependency injection for the twig_js assetic filter

As of now, there is an issue preventing the Assetic from loading the filter if the name of the service associated to the filter doesn't respect the assetic.filter.filter_name convention.

    [Symfony\Component\DependencyInjection\Exception\ServiceNotFoundException]                                
    The service "assetic.asset_factory" has a dependency on a non-existent service "assetic.filter.twig_js".

This code fixes that issue, by renaming the twig_js.assetic_filter service into assetic.filter.twig_js