RedisProfilerStorage wrong db-number/index-number selected

bug: in the webprofiler the wrong database (0) is selected when storage should not go to index 0. on redis connect the default behaviour is to select index/database number 0, but it is necessary to select a special index/database.
see: http://rediscookbook.org/multiple_databases.html

[HttpKernel] [Profiler] [RedisProfilerStorage] added select for a db-number/db-index to dsn-patttern

| Q             | A
| ------------- | ---
| Bug fix?      | [yes]
| New feature?  | [no]
| BC breaks?    | [no]
| Deprecations? | [no]
| Tests pass?   | [yes]
| Fixed tickets | 
| License       | MIT

Usage with index/db-number = 7 :
```xml
<!-- config_dev.xml -->

<symfony:profiler only-exceptions="false" dsn="redis://127.0.0.1:6379/7" lifetime="3600" />

```

```yml
#config_dev.yml

framework:
...
    profiler:
    ...
        dsn: redis://127.0.0.1:6379/7

```