Expand normalizeUserAttributeMap

I have refactor method `normalizeUserAttributes` to expand for `normalizeUserAttributeMap` and add example for config client.
Please review. If you think that is reasonable please merge it and complete docs for it.

Thanks
I am unsure it is a good idea to support such syntax.
Perhaps it whould be better to use simple array of keys instead:
```php
['languages', 0, 'name']
```
After all, '/' symbol may be used as part of plain attribute name.