webglapp.js: implement missing function refresh_skeletons for the update button.
webglapp.js: implement missing function refresh_skeletons for the update button.

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