merge attempt

ChangeLog

demos/Wiener_Filter.ipynb

demos/bench_gridder.py

demos/bernoulli_demo.py

demos/getting_started_1.py

demos/getting_started_2.py

demos/getting_started_3.py

demos/getting_started_mf.py

demos/polynomial_fit.py

nifty6/__init__.py

nifty6/extra.py

nifty6/library/special_distributions.py

nifty6/minimization/metric_gaussian_kl.py

nifty6/minimization/metric_gaussian_kl_mpi.py

nifty6/mpi.py

nifty6/operators/operator.py

nifty6/random.py

setup.py

test/common.py

test/test_energy_gradients.py