merge master

demos/critical_filtering.py

demos/wiener_filter_via_curvature.py

demos/wiener_filter_via_hamiltonian.py

nifty/basic_arithmetics.py

nifty/config/nifty_config.py

nifty/energies/energy.py

nifty/energies/line_energy.py

nifty/field.py

nifty/library/wiener_filter/wiener_filter_energy.py

nifty/minimization/descent_minimizer.py

nifty/minimization/line_searching/line_search.py

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

nifty/operators/fft_operator/fft_operator.py

...y/operators/fft_operator/transformations/rg_transforms.py

...rators/fft_operator/transformations/rgrgtransformation.py

nifty/spaces/rg_space/rg_space.py

nifty/sugar.py

nifty/version.py

setup.py

test/test_field.py