Regions of interest: add editor field to model
Regions of interest: add editor field to model

This field was somehow forgotton in the past. And since we recently
added a NOT NULL constraint on this field, no new regions of interest
could be created. This commit fixes this problem.

Thanks to Felix von Zadow (@fzadow) for making me aware of this.

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