Saving and loading of a mapping configuration done (save for showing an error messagebox when a loaded configuration is not valid)

# Conflicts:
#	arthropod_describer/plugins/pekar_unet/regions/pekar_unet/utils/model.pt

# Conflicts:
#	arthropod_describer/app.py
#	arthropod_describer/tag_filter_widget.py

Made parsing GLCM parameters a more robust (should ignore non-numeric parts of the strings or consecutive commas)

when the main window becomes inactive do not show filter tags (solves the disappearance of plugin browser, but not completely - when hovering tags list for individual images, it can still disappear)

LabelHierarchy: added a method to retrieve all child nodes/labels of a node/label + used it in `pekar_unet.segmentation.py` `__call__` method