Refactored assignment delete view to a class based view

Refactored set_status, run, delrun, delother and setactive from assignments to class based views.

Refactored set_publish_status and assignment_gen_poll to be class based views.

Refactored set_elected of assignment to a class based view

Unified the use of assignment_id / pk in assignment views

Refactored edit and create view from assignments to be class based views.

Merged with master.

Refactored view function of assignment to class based view.