Fixed language file import problem: https://www.howtoforge.com/community/threads/import-language-issue.70355

-Added a new option "Network Filesystem" under System > Server config > Web to toggle on / off the _netdev option for the bind mounts in /etc/fstab

- Merged language files

- Create md5 sums of all files at install and update.

- Added warning in the interface when a path for a shelluser is set that is outside of the website docroot.
- Added security settings feature to allow the root user of a server to control most aspects of whet the admin user of the controlpanel is allowed to do in system settings. This is especially useful for managed severs where the ispconfig admin user and the root user of the server are different persons.

Removed backup_dir_mount_cmd option from Sysstem > server config. The option has been replaced by a script /usr/local/ispconfig/server/scripts/backup_dir_mount.sh. If this script exists, is exacutable and is owned by the root user, then it will be executed upfront of the backup jobs when the option "Backup directory is a mount?" is enabled in server config settings.

- Fixed: nginx placeholders could not be added to directive snippets textarea by clicking on the link.

Fixed regex in prefix validation under System > interface config that prevented numbers in prefixes.

- Added missing option in centos dovecot.conf file

- Updated version number to 3.0.5.4rc1

- Updated Linux Distribution detection to recognize all wheezy sub versions correctly.

This reverts commit 4cd62d78.

- Use it like $app->conf('yourpluginname', 'config-key', 'value')
- omit the value to read the config value, provide it to set the value