Ok I found it and tried to upgrade manually. Now nothing works. I'm afraid i've damaged the database. I have backups of course, but the upgrader doesn't work...
I guess installing a clean 1.6 version would be the best solution... But I have a lot of projects and documents in my Opengoo that I don't want to delete. Is there any way I can install 1.6 and fill the old data into it without ruining the database?