fixed small bug in mail-backup-cron

Fixed error in Mail-Backup-Cron-Task (created file /dev/nul - missing l)

additional added mail_backup to webspace-quota if mail and webdomain are on the same server
changed backup-filesize from formated string to byte-count, because of low-level-remote functions

Removed possibility of reinstalling Instances

- Added HHVM to "Default PHP Handler" field (server configuration).
- Fixed "Unable to load the server configuration from database." error when running server.sh.
- Fixed Javascript (accordions weren't working anymore, directive snippets and other placeholders couldn't be added anymore).