Npdyn

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Minor bug fixes

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Major change for dataset handling, the new class 'Sample' is now used. It is
essentially a NumPy array with extra attributes and methods for data correction
and fitting.
The class 'Dataset' has been removed.
Replacing the 'QENSPlot' and 'FWSPlot' windows by only one 'Plot' class.
Adding the possibility to use the z-direction on the position-sensitive
detectors as an observable.
Adding and optimizing data reduction for BATS data recorded on IN16B at the ILL.
Adding new built-in models.
Adding a 'slidingAverage' capability along the observable.
Adding support for diffraction data on IN16B.
Adding helper functions for use with molecular dynamics simulation data and
for generating Stokes-Einstein curves.
Some bug corrections and code quality improvements.

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Fixing an issue with lmfit backend, which makes use of the inverse errors
and not the errors as previously passed by nPDyn.

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The version introduces the builtin Model interface feature as well
as the interface with the lmfit package as backend for data fitting.

In addition, data structure was changed as compared to v1.0 and
simplified. There is only a 'QENSType' and 'FWSType' now, for which
the 'data' attribute contains new entries.

For both 'QENSType' and 'FWSType', the intensities and errors are 3D
numpy arrays where the first axis correspond to the observable, the
second to the momentum transfer q-values and the last to the energies.

For the package structure itself, most of the files were moved to the root
and the actual nPDyn code is in the 'nPDyn' directory in root.

It includes new tests and more extensive documentation.

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Initial version of nPDyn.
We keep track of it as it has been used for some publications.