Fixed/Implemented: replaced intval() by $app->functions->intval() in all interface functions due to big number problem in intval()

Added Support for Sieve mail filtering language on dovecot servers.

Data records are now assigned to the correct client group if they were created by the administrator.

This is to try to fix the bug where if a filter is created by an admin, then the user with the e-mail account can't see the filter. 

http://bugtracker.ispconfig.org/index.php?do=details&task_id=267&string=&project=3&search_name=&type[0]=1&sev[0]=&pri[0]=&due[0]=&reported[0]=&cat[0]=&status[0]=open&percent[0]=&opened=&dev=&closed=&duedatefrom=&duedateto=&changedfrom=&changedto=&openedfrom=&openedto=&closedfrom=&closedto=

- Updated Debian installation instructions.

- Better Autoresponder script
- Fixed error in language file.

- fixed bugs when websites and dns zones were deleted.

- Changed shell of website linux user to /bin/false