Napari-assistant

Bugfix
* Button icons were not shiped with the installation package

Bugfixes
* Use setup.cfg instead of setup.py for improving conda build

Bugfix
* Measurments didn't work via the assistant because there was no run button

Bugfix
* Error when search field was empty

Bugfixes
* Dependency to napari-time-slicer was outdated leading to crashes

New features
* Undo/Redo functionality for workflows (big thanks to Cryaaa !)

Bug fixes
* Improved compatibility with dask-array backed layers
* Reduced re-execution of operations when updating parameters