bug in installer

[Saro Engels]

There is a small bug in the installer:
If I install packages which are downloaded from somewhere else, they are 
not shown as installed.
I haven't made a patch yet, I think we need to make something like a 
registry test for installation (if there is no system interaction with 
the registry, we can simply make up a package). This probably needs to 
be included in the config.txt file since we probably cannot guess it.

SE