Nose tests are not uniform

Created by: siebenkopf

I just noticed that the usage of nose tests is not uniform. Sometimes, the unittest framework is used, and sometimes the nose framework. After discussion with anjos we found that the nose tests have more pros, and hence, we should try to port all nose tests to nose (removing the dependence to the unittest.TestCase class).

This bug has low priority since it is just a unification of tests.