Add the number of characters into username
 

Add an option to ispmgr.conf to be able to use more characters in a username (now you cannot provide more than 16 characters), because almost all Linux-based systems allow system user names 32 characters long. Allow more characters in FTP user names (ftp servers support not less than 30 characters). This will be useful, when importing users from other panels or if a domain is used as a user name.