Implemented group graph widget.
Fix issue destroying OptionDialog instances: they weren't before.
Merge remote-tracking branch 'origin/master' into group-graph

Conflicts:
	django/applications/catmaid/static/widgets/compartment_graph_widget.js
	django/applications/catmaid/static/widgets/graph_plot.js
Group Graph: Fix error with creating Hex colors for coloring nodes.
Group Graph: enable coloring by own or union of reviews.