Improvement: Add unix_socket to dsn variables in PDO Adapter

[KIVagant]

Sorry for my bad English.

Now, for connection to db through unix socket I need setup $dsn string manually as full string in config. It's not good, because I need to make some logic in configuration file.
I propose to add this lines to src/Adapter/Driver/Pdo/Connection.php after #239 row:

                    if (isset($unix_socket)) {
                        $dsn[] = "unix_socket={$unix_socket}";
                    }