Advocate signoff feature. Integrated with operator signoff.

gracedb/api.py

gracedb/forms.py

gracedb/migrations/0007_auto_new_signoff_model.py

gracedb/migrations/0008_add_advocate_labels.py

gracedb/models.py

gracedb/query.py

gracedb/urls.py

gracedb/urls_rest.py

gracedb/view_utils.py

gracedb/views.py

migrations/auth/0008_add_advocates.py

settings/default.py

templates/gracedb/event_detail.html

templates/gracedb/event_detail_script.js