Client connector trait to convert request params and files into PHP form

PHP has very strange format for $_FILES superglobal array if form field name contains square brackets. This code convert BrowserKit\Client files format into PHP-compatible one.
PHP request parameters and files high-level names can not contain dots or spaces and PHP converts all of them into underscores. So we have to convert all that as well.


see https://github.com/symfony/symfony/issues/6908 
https://github.com/symfony/symfony/pull/10444 
https://github.com/symfony/symfony/pull/10193 
https://bugs.php.net/bug.php?id=25589 
https://bugs.php.net/bug.php?id=25589