Changed unmarshalling integration test to use parametrized unit tests and a separate coverage test

The famous WillItUnmarshall unit test now uses some parametrized test magic to make the integration tests for the configuration files more easy.

Using this method, a new configuration file can be added by adding one single line of code and a new test instance for this file is created automagically.

This also moves the test coverage mechanism for the old version to a separate class, testing the coverage of the WillItUnmarshall test. This meta test also uses the parametrized test feature to provide a test instance for each file in the /etc directories checking the coverage for this file and providing a clean test failure if the file is not covered.