Furthermore, the zero_mode keyword is gone for AmplitudeOperator. It is not used
in the demos and is not really appropriate from a theoretical point of view
anyways. We will add in a better option later.

People who would like to check in pngs can still do it with the help of a
force-stage. Since we do not want to have pngs in the repository generally it is
sensible to have it in the gitignore file.

Multiplication of operators had worked before. Only multiplication with scalars
was not possible.

dynamic and light cone prior

See merge request ift/nifty-dev!152

mtr documentation

See merge request ift/nifty-dev!160

Switch to napoleon only

See merge request ift/nifty-dev!163

Merge branch 'move_dynamic_prior' of https://gitlab.mpcdf.mpg.de/ift/nifty-dev into move_dynamic_prior

removed duplicate inverse

See merge request ift/nifty-dev!162

Migrate to pytest

See merge request ift/nifty-dev!159