more DomainTuple work

nifty2go/__init__.py

nifty2go/domain_tuple.py

nifty2go/field.py

nifty2go/nifty_utilities.py

nifty2go/operators/composed_operator/composed_operator.py

nifty2go/operators/diagonal_operator/diagonal_operator.py

nifty2go/operators/fft_operator/fft_operator.py

nifty2go/operators/laplace_operator/laplace_operator.py

nifty2go/operators/linear_operator/linear_operator.py

...y2go/operators/projection_operator/projection_operator.py

nifty2go/operators/response_operator/response_operator.py

...operators/smoothing_operator/direct_smoothing_operator.py

...go/operators/smoothing_operator/fft_smoothing_operator.py

...y2go/operators/smoothness_operator/smoothness_operator.py

nifty2go/probing/prober/prober.py

test/test_field.py