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).

- Fixed: FS#3710 - Bug with PHP-FPM configuration since 3.0.5.4 Patch 4
- Fixed wrong function calls in system lib.

- Fixed a problem with restart of services due to the fact that Ubuntu has upstart and systemd installed, but only upstart is working without errors.