devilry_gradingsystem.pluginregistry: Require deliveryid for get_edit_feedback_url().
devilry_gradingsystem: Added sets_max_points_automatically.
docs.devilry_gradingsystem: Cleanup.
core.models.assignment: Created grading setup helpers that reflect how the system works.
devilry_gradingsystemplugin_points.devilry_plugin: Implemented the plugin API.