merge NIFTy_5

README.md

docs/source/ift.rst

docs/source/index.rst

docs/source/installation.rst

nifty5/domains/domain.py

nifty5/fft.py

nifty5/linearization.py

nifty5/minimization/energy.py

nifty5/minimization/iteration_controllers.py

nifty5/minimization/line_search.py

nifty5/minimization/minimizer.py

nifty5/operators/block_diagonal_operator.py

nifty5/operators/energy_operators.py

nifty5/operators/operator.py

nifty5/probing.py

nifty5/sugar.py

nifty5/utilities.py

setup.py

test/test_multi_field.py

test/test_operators/test_fft_operator.py