Add cascade delete and fix db nullability
Add cascade delete and fix db nullability
Merge remote-tracking branch 'origin/feature/cascade_delete' into feature/cascade_delete

Conflicts:
	src/ggrc/models/directive.py
	src/ggrc/models/program_directive.py
	src/tests/ggrc/models/factories.py
	src/tests/ggrc/models/test_cascade_delete.py
Add cascading delete behavior to remaining models
Add unique constraint to control_assessment
Add cascade delete and fix db nullability
Add cascade delete and fix db nullability
Add cascading delete behavior to remaining models
Add unique constraint to control_assessment
Merge remote-tracking branch 'origin/feature/cascade_delete' into feature/cascade_delete
Remove remaining references to Transaction model
Allow nulls for control.directive_id
Fix behave tests for cascading deletes and NOT NULL columns

* add `_publish_attrs` for RiskRiskyAttribute
* remove `Transaction` cases for behave tests
* add FactoryStubMarker to fill in required linked resources
* change post_example(...) to recursively POST to make valid links
Add step to autocreate permissions for related resources
Remove feature that is subsumed by links_m_to_n
Merge remote-tracking branch 'origin/develop' into feature/cascade_delete_tests

Conflicts:
	src/ggrc/models/event.py
	src/ggrc/models/section.py
	src/service_specs/permissions.feature
	src/service_specs/steps/ggrc_http.py
	src/tests/ggrc/behave/utils.py
Fix permission tests to create related objects in the same context as example object
Merge branch 'develop' into feature/cascade_delete_tests
Invert condition around 'selected' attribute
Update test-running scripts for ggrc_basic_permissions

* also added nosetests