New global option to grant reseller users access to the options (advanced) tab in web domains and vhost subdomains

Implemented checkboxes in Interface Config to enable showing/hiding the tabs Mail Filters, Autoresponders and Custom Rules for mailboxes.

See also http://www.howtoforge.com/forums/showthread.php?t=59539

- need to have the pecl idn and intl modules installed
  or
- have the idna_convert class in the classes/idn/ path

Implemented:  FS#2388 - Optional confirm window on changing tabs

http://bugtracker.ispconfig.org/index.php?do=details&task_id=1689

Using these variables in welcome email from admin, when mailbox is created.

Added a new module called "domain". With this module you can manage all domains (web + mail). Per default this module is not active. To activate it, you have to change the System Interface Config -> domains -> use the domain module. You also have to activate the domain-module for the admin (and for every client if you want). Important: you can not use this module if you have reseller!

- Formatted error messages for better visibility.