Fix typos, path to file which was moved and renamed and replace "which mdadm" call to file_exist('/proc/mdstat') as we are not using mdadm in this script anyway.

Implemented: FS#1252 - Add permission system based on user / password to app installer 

Fixed: FS#1229 - ISPConfig3 creates the desired e-mail domain twice (on master server AND on the selected Slave) 

- Fixed a formatting problem with suphp.conf and newer suphp versions.

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Merged revisions 1832-1836 from stable (added dovecot support for debian squeeze and added a new distid and class for debian6 specific modifications.

The "new" php session-cleaning source works fine for several days at my servers, so we can delete the old (not working) one