Create LabelSet model the right way.

[#46033489]
setup default permissions for LabelSets
Whitespace in activity.rb
Mark LabelSets as children of the activity
Try to get a "new for activity" link for LabelSets
Merge branch 'master' into wip-label-sets

Conflicts:
	app/controllers/label_sets_controller.rb
	app/models/label_set.rb
	db/schema.rb
	spec/controllers/label_sets_controller_spec.rb
	spec/helpers/label_sets_helper_spec.rb
	spec/models/label_set_spec.rb
Rename 'Label' to 'GraphLabel'

Speculative fix - is there a name collision in Hobo with the 'Label' model which is causing my headaches?
Bug fixes to make label sets work with labels.