devilry_examiner...allgroupsoverview_base: Show warning if no deliveries

and waiting for feedback.
devilry_examiner...forms.less: Added a class for truly inline forms.

The default form-inline bootstrap class renders the form as a "block".
Added a class that renders the form as "inline-block". Perfect when
showing multiple buttons in a row, each with their own form.
devilry_examiner...give_another_chance_question: Decouple the add deadline form.

This is also needed by #519.
devilry_examiner: Started on the UI for #519.
devilry_examiner...bulkviewbase: Updated to use POST only.

No sessions, and no GET data. Updated add deadline view with the changes.
devilry_examiner...bulkviewbase: Set optionsdict and selected_groups

in the template context.
devilry_examiner...bulkviewbase: Document the properties.
devilry_examiner...add_deadline: Render selected groups correctly.
devilry_examiner...add_deadline: Use the correct submit name.
devilry_examiner...test_add_deadline: Cleanup _post_as().
devilry_examiner...add_deadline_on_single_group: Use POST.
devilry_examiner.urls: Pep8 format.
devilry_examiner.urls: Cleanup and removed i18n javascript view.
devilry_examiner...bulkviewbase: Validate the optionsform BEFORE checking cancel.
devilry_examiner...test_add_deadline: Test urls.
devilry_examiner...add_deadline: Include urls as hidden fields in form.
devilry_examiner...test_add_deadline: Check that submit buttons render.
devilry_examiner.views.close_groups: Usable.
apps.core.models.assignment_group: Added close_groups() to the manager.
devilry_examiner...close_groups: Cleanup the layout.