Merge branch 'quality' into dev

api/permissions.py

api/urls.py

api/views/__init__.py

api/views/datasources.py

api/views/quality.py

datasources/admin.py

datasources/forms.py

datasources/migrations/0032_add_quality_rules.py

datasources/migrations/0033_quality_levels_ordered.py

datasources/models/__init__.py

datasources/models/datasource.py

datasources/models/metadata.py

datasources/models/quality.py

datasources/serializers.py

datasources/static/js/metadata.js

datasources/templates/datasources/datasource/detail.html

datasources/templates/datasources/datasource/list.html

datasources/templates/datasources/datasource/metadata.html

datasources/templatetags/__init__.py

datasources/templatetags/datasource_extras.py