Fix permissions issue preventing icingaweb2 from reading the backend config and add preferences DB
The /etc/icingaweb2/modules directory ends up with "drwxrwSrwx" permissions, missing the "x" bit preventing icingaweb2 from reading the monitoring backend configuration in /etc/icingaweb2/modules/monitoring/. Instead of adjusting single files and directories, enforce sensible permissions on all directories and configuration files.
Also, starting with version 2.11 user preferences must be stored in the DB.