params registered, sample modified (log-det), gitignore modified

- Registered params in log-det classes private init method
- CLogDetEstimator::sample modified (does not rely on sample_without_averaging anymore)
- NormalSampler uses CRandom::std_normal_distrib instead of CMath::randn_double
- unit-tests updated
- .gitignore file updated to ignore serialization unit-tests files