enh: Create separate average for each segmentation label [Applications] (#628)
enh: Create separate average for each segmentation label [Applications] (#628)

* enh: Create separate average for each segmentation label
* doc: Fix help of average-images
BioMedIA/MIRTK,BioMedIA/MIRTK,schuhschuh/MIRTK,BioMedIA/MIRTK,BioMedIA/MIRTK,schuhschuh/MIRTK,schuhschuh/MIRTK,schuhschuh/MIRTK