Merge branch 'NIFTy_5' into adjust_variances_but_right

demos/bernoulli_demo.py

demos/getting_started_2.py

demos/getting_started_3.py

demos/polynomial_fit.py

nifty5/__init__.py

nifty5/extra/energy_and_model_tests.py

nifty5/library/inverse_gamma_model.py

nifty5/linearization.py

nifty5/minimization/conjugate_gradient.py

nifty5/minimization/descent_minimizers.py

nifty5/minimization/energy.py

nifty5/minimization/energy_adapter.py

nifty5/minimization/kl_energy.py

nifty5/minimization/quadratic_energy.py

nifty5/minimization/scipy_minimizer.py

nifty5/operators/energy_operators.py

nifty5/operators/linear_operator.py

nifty5/operators/operator.py

nifty5/plotting/plot.py

test/test_minimization/test_minimizers.py