A test in kdev-ruby fails, and the root problem is that
TestProjectController destroys some of the semantics of its
ProjectController base. ProjectController isn't able to delete projects
in such cases => leads to strange issues in the end.
Fix for good: Remove TestProjectController, and add a little more API to
IProject & IProjectController which we can access from unit tests.
Also leads to a cleaner implementation of
ProjectController::closeProject (no cast to Project* needed anymore).