more safe merges from dobj_experiments

nifty/basic_arithmetics.py

nifty/domain_tuple.py

nifty/energies/line_energy.py

nifty/low_level_library.py

nifty/minimization/conjugate_gradient.py

...ization/iteration_controlling/gradient_norm_controller.py

...y/minimization/line_searching/line_search_strong_wolfe.py

nifty/operators/composed_operator.py

nifty/operators/response_operator.py

nifty/operators/smoothness_operator.py

nifty/plotting/plot.py

nifty/spaces/lm_space.py