Confirmation question before joining other skeleton with more than one node
Confirmation question before joining other skeleton with more than one node

Closes #304

fzadow/CATMAID,fzadow/CATMAID,htem/CATMAID,htem/CATMAID,fzadow/CATMAID,htem/CATMAID,htem/CATMAID,fzadow/CATMAID