Show warning message someone tries to use root as username for a client database when the database prefixes are removed.

Fixed: FS#913 - Adding a new database user and table through the webgui and leaving the allowed IP fields empty for 

- changed GRANTs for slave servers on multiserver setups
- added option for clients to change path of ftp users (inside webroot)
- extended software packaging system (return status of install)
- added 2 plugins for automatically create symlinks webmail and phpmyadmin on each website (not enabled by default)

- Improved installer and updater for multiserver mode. Modules and plugins were only configured if the selected service is available on the server.

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- Updated Debian installation instructions.