... and more cleanups

demos/polynomial_fit.py

nifty5/domains/dof_space.py

nifty5/domains/domain.py

nifty5/domains/gl_space.py

nifty5/domains/hp_space.py

nifty5/domains/lm_space.py

nifty5/domains/log_rg_space.py

nifty5/domains/power_space.py

nifty5/domains/rg_space.py

nifty5/domains/unstructured_domain.py

nifty5/library/los_response.py

nifty5/minimization/descent_minimizer.py

nifty5/minimization/energy.py

nifty5/minimization/gradient_norm_controller.py

nifty5/minimization/line_energy.py

nifty5/minimization/scipy_minimizer.py

nifty5/operators/block_diagonal_operator.py

nifty5/operators/central_zero_padder.py

nifty5/operators/chain_operator.py

nifty5/operators/diagonal_operator.py