Use Arquillian instead of mocks

[AlistairDoswald]

Currently the WS-Fed code is tested with Mockito for all data that would be coming from keycloak or the database. However, in the Keycloak project they use Arquillian to test their protocol functionalities. In order to bring our testing procedures closer to theirs, we should also use Arquillian.

The current tests should thus be replaced with tests showing the same functionalities, but using a "real" keycloak instance through Arquillian, rather than using mocks.

[AlistairDoswald]

Once Arquillian is set up, we should see if it is possible to automatically test the GUI as well.

[lagess]

Some unit tests should be move to arquillian, but maybe not all of them. This is to be analyzed.
Arquillian is now set up for nominal cases coverage. They still have to be extended to cover more use cases.