Instead of going away from Preferences to Properties (the former being supposedly the more modern option), I've now added a way to customize the preference node to which the setting is stored.
Right now it is the same for all test runs, we could change that to some random sub-node. In that case, however, we should look into cleaning the preference store before closing test instances and we have to keep in mind that it would not allow to test persistency of settings in test builds.
Based on !236 (merged)
Closes #350