Adding 'auto_approve' to client details array (with updated interface docs)

While following https://github.com/php-loep/oauth2-server/wiki/Developing-an-OAuth-2.0-authorization-server I noticed in the authorize method the reference to `auto_approve` in this line 

    // Check if the client should be automatically approved
    $autoApprove = ($params['client_details']['auto_approve'] === '1') ? true : false;

We add the field to the database in the sql however we don't return it with the client_details array. This patch fixes it.