Likeness: Support for deep properties in WithDefaultEquality

See #48

Changes:

- New method `ToDeepEvaluator`. Used in `WithDefaultEquality` instead of `ToEvaluator`. This new method mimicks the behavior of `ToEvaluator`. A re-use of `ToEvaluator` inside `ToDeepEvaluator` was not feasible.
- Added two unit tests to verify the behavior on sub-properties.
- Existing unit tests continue to succeed --> Existing functionality has not been changed.