Changing regex for dns_ns to allow delegating LE requests to seperate nameservers

For upcoming wildcard certificates from Let's Encrypt it would be nice to delegate LE (dns-challenge) requests to a seperate nameserver like: _acme-challenge.example.com. NS ... ns2.exmaple.com.

Therefore it is needed to change the regex for /ispconfig3/interface/web/dns/form/dns_ns.tform.php from:

'validators' => array ( 0 => array ( 'type' => 'REGEX', 'regex' => '/^[a-zA-Z0-9\.\-]{0,255}$/', 'errmsg'=> 'name_error_regex'), to

'validators' => array ( 0 => array ( 'type' => 'REGEX', 'regex' => '/^[_a-zA-Z0-9\.\-]{0,255}$/', 'errmsg'=> 'name_error_regex'),