Unify naming

ChangeLog.md

demos/bernoulli_demo.py

demos/getting_started_2.py

demos/getting_started_3.py

demos/getting_started_5_mf.py

demos/getting_started_density.py

demos/parametric_variational_inference.py

demos/polynomial_fit.py

docs/source/code.rst

src/__init__.py

src/library/adjust_variances.py

src/operators/energy_operators.py

src/operators/operator.py

src/sugar.py

test/test_energy_gradients.py