Improved client and reseller limit checks

Fixed: FS#810 - FTP - If username is left blank and client clicks options a clientname_ blank username is created.

Fixed: FS#787 - A sub-client can see all the clients on the system in the client drop down list 

Fixed FS#775 - Client can choose the servers for it's client 

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Changed: separate crontab files for chrooted and other cron jobs

Fixed: Missing server.ini config entries for vlogger and jailkit
Added: Admin interface server_config for vlogger and cron

Fixed: FS#778 - mailalias has priority over mailbox if they both exist. Added a error message that prevents it to add a alias or forward when a mailbox with the same email address exists.