webglapp: create the graph of each skeleton on demand only rather than by default when reinit_actor.
webglapp: create the graph of each skeleton on demand only
rather than by default when reinit_actor.

This helps reduce memory usage; the jsnx.Graph is heavy.

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