Merge branch 'nifty6to7' into 'NIFTy_7'

demos/getting_started_4_CorrelatedFields.ipynb

src/__init__.py

src/library/correlated_fields.py

src/minimization/metric_gaussian_kl.py

src/operators/normal_operators.py

src/random.py

src/utilities.py

test/test_operators/test_jacobian.py

test/test_operators/test_normal_operators.py