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
Added missing fields (and slight redesign) of Roles modal
improved create new program visually
Add step to autocreate permissions for related resources
Remove feature that is subsumed by links_m_to_n
Added missing fields (and slight redesign) of Roles modal
improved create new program visually
Display an Authorizations section in the program page for private
programs for users that have the permissions required to edit role
assignments.

Also, establish a pattern for loading extension blueprints; this was
necessary to add the Authorizations section.

Also, fix the styleguide so that modals work.