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!

Removed some unmaintained tables and files and introduced the pre_update.sql script for sql commands to be run before an update.