devilry_subjectadmin.rest: Fixed the node-breadcrumbs for superusers.
devilry_subjectadmin: Fixed nodeadmin/superuser breadcrumbs.
devilry_subjectadmin: No dashboard link, and include "my" in "all courses".

This works far better when users are node admin and course admin at the
same time, and it removes a part from a sometimes very long breadcrumb.
devilry_nodeadmin: No default breadcrumb.
devilry_student: No default breadcrumb.