[PROFILER][REDIS] Support database, auth on redis connection

Bug fix: no
Feature addition: yes
Backwards compatibility break: no
Symfony2 tests pass: yes

Allow database and password on dsn:

```yml
framework:
    profiler:
        dsn: redis://127.0.0.1:6379
        dsn: redis://127.0.0.1:6379/3
        dsn: redis://user:password@127.0.0.1:6379/3
```

Since redis uses only password for authentification, user will not be used ...