[OPENENGSB-3603] added tests to EDBConverterTest and EDBIT for cascading...

... models

so as it turns out, cascading and recursion with models does in fact work and no changes were required [1]

however i wrote some more rigorous tests for this, so we can safely refactor the EDBConverter according to  [OPENENGSB-2719].

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  [1]: http://issues.openengsb.org/jira/browse/OPENENGSB-3603
  [OPENENGSB-2719]: http://issues.openengsb.org/jira/browse/OPENENGSB-2719