Napari-pyclesperanto-assistant

New features
* Statistics of labeled pixels including distance to neighbors (based on [napari-clusters-plotter](https://github.com/BiAPoL/napari-clusters-plotter) code by Cryaaa and lazigu)
* Neighborhood statistics (minimum/mean/median/maximum/standard deviation of measurements of neighboring objects)
* New category: Combine labels (via [napari-assistant](https://github.com/haesleinhuepf/napari-assistant) & [pyclesperanto-prototype](https://github.com/clEsperanto/pyclesperanto_prototype))

Bug fixes
* GPU-selector didn't work

Backwards compatibility breacking changes
* The clesperanto-based Assistant GUI was removed from the menu. Use `Tools > Utilities > Assistant (na)` instead

New features
* Use the napari-assistant as new graphical user interface

Backwards compatibility breaking changes
* The Assistant class and related functions have been moved to the napari-assistant repository
* `statistic_of_labeled_pixels` now uses a label image as second parameter and no label-layer anymore
* Jython code generation is not available temporarily. Use the python code generator and adapt the code manually in Fiji

Bugfix:
* `divide_image` from napari-segment-blobs-and-things-with-membranes caused error when called from the assistant, when only one image was opened (thanks to Cryaaa for reporting 51 )

New features
* Increased button size (for touch-screen users with thick fingers)
* Reduced gap between buttons
* Added temporary spinner for tuning button size

Bug fixes
* Thanks to multi-line text in combo boxes operation names should now be readable also on Windows

Bugfix
* Widgets were requesting too large space (Thanks to psobolewskiPhD for reporting)