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

 - added configuration options to server config (web tab, php section)
 - do not update custom php.inis if md5sum file does not exist

Added: Changed idn function to support multi-line fields (like mail forward)

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

Bugfix: Attachments were not cleaned up on finish() call of mail class (next recipient gets all attachments, too)
Update: some import tests for plesk