Add a comprehensive test-suite

[domi41]

We're going to use JSON files for this.

For reference, the JSON file to fill is here : https://github.com/MieuxVoter/majority-judgment-library-java/blob/master/src/test/resources/assertions.json

We already have a bunch of tests, but we need more.

[domi41]

Close this once we have added the test with real data from real-world experiments.