Napari-simpleitk-image-processing

Documentation update

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

Bugfix:
* `label_statistics` caused an error when called from scripts and no viewer was provided

New features
* label_statistics
* simple_linear_iterative_clustering
* scalar_image_k_means_clustering
* invert_intensity
* adaptive_histogram_equalization
* curvature_flow_denoise
* morphological_gradient
* standard_deviation_filter
* relabel_component
* label_contour
* threshold_intermodes
* threshold_kittler_illingworth
* threshold_li
* threshold_moments
* threshold_renyi_entropy
* threshold_shanbhag
* threshold_yen
* threshold_isodata
* threshold_triangle
* threshold_huang
* threshold_maximum_entropy

Added `__common_alias__` and simplified API for better code generation.

Backwards compatible changes
* Changed menu entries to cover finer differentiation between various filtering and segmentation techniquese