Correctly compare lists of lists with `$in`.

This pull requests adds the functionality to compare lists of lists with the `$in` operator in fongo.

The query `{"a" : {"$in", [[1, 2]]}}` will match the result `{"a" : [1, 2]}` but not `{"a" : "1"}` or `{"a" : "2"}`. The current implementation will match non of these objects which is not the behavior of mongo.

* Fix for comparing list of lists with `$in`
* Unit test to verify correct behavior
* `@Override` and `@SuppressWarning("javadoc)"` in `ExpressionParser`

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@hoffrocket / @twillouer please review, merge and delete the branch.