add discard mechanism

atdb/taskdatabase/templates/astronauth/navbar.html

atdb/taskdatabase/templates/taskdatabase/archived/tasks.html

...askdatabase/templates/taskdatabase/discarded/headers.html

atdb/taskdatabase/templates/taskdatabase/discarded/page.html

.../taskdatabase/templates/taskdatabase/discarded/tasks.html

...base/templates/taskdatabase/failures/confirm_discard.html

atdb/taskdatabase/templates/taskdatabase/failures/tasks.html

atdb/taskdatabase/templates/taskdatabase/index.html

atdb/taskdatabase/templates/taskdatabase/tasks.html

...skdatabase/templates/taskdatabase/tasks/details_card.html

atdb/taskdatabase/urls.py

atdb/taskdatabase/views.py