Fixes Encoding to UTF-8 and Add Some New Strings

Deleted the client id check, now he goes directly to the sysuser_id. Now you don't have to use the client id anymore, only more the sysuser_id. Solves issue when client has more than one sysuser

Added a option to debug the language files (show strings that are not contained in the lang file surrounded by #....#)
Fixed: FS#1063 - Missing language variables in shell user options 

Fixed general utf8 encoding problems when data is passed from frontend to server, this fixes also bug FS#1065 - Special characters in autoresponder subject may break the autoresponder 

Merged all language files.

Additionally fixed a bug in web quota calculation.

Implemented: FS#1049 - Allow "Login as" also from the client list as it is allready possible from sysuser list.

Fixed: FS#1012 - Delete all records (domains, ftp users, etc.) of a client when the client gets deleted.

Added a global default for the .htaccess allow_override setting.

Changed the characters that are available to be used in the password salt to avoid decoding problems with certain 64Bit Linux systems.