Added parameters default values for service config

Symfony 2.2, php 5.4
W/o existense of next parameters cannot use this bundle

  [Symfony\Component\DependencyInjection\Exception\ParameterNotFoundException]
  The service "rollerworks_password_strength.blacklist.provider.sqlite" has a dependency on a non-existent parameter "rollerworks_password_strength.blacklist.sqlite.dsn".

  [Symfony\Component\DependencyInjection\Exception\ParameterNotFoundException]
  The service "rollerworks_password_strength.blacklist.validator" has a dependency on a non-existent parameter "rollerworks_password_strength.blacklist_provider".