Added dns_zone_get_id function get id from domain name. To discover a domain id passing domain name as argument.

use the standardize app->db->quote method already established.

Refs: 1722

Also removed the calls to the db closeConn calls in favor of
destryong the connections on the class __destruct() 's..

Since firebird db had a closeConn as well, changed its __destruct
to calls its own personal closeConn which otherwise left unmodified.

Refs: 1722

- Fixed UTF-8 support in email function.

  @param  -> session_id
  @return -> Array of all Client IDs on server

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Fixed: PHP notice in tform_actions.inc.php

- Added a new IP validator to the tform library which validates IPv4 and IPv6 addresses.

Undone the deletion of the config.inc.php file. It is intended that the file is there as dummy and gets replaced during installation.

- Added a function to the remote api to get all virtual machines of a client.

Added destructor and session write to app class instead.

http://bugtracker.ispconfig.org/index.php?do=details&task_id=1671