Implement extensions to the grading API so that modules can store their grades "directly" in the gradebook (without actually accessing gradebook classes)

1) some way for an activity to request HTML form fragments that contain the relevant popup menus for all the associated outcomes.
2) some way to submit the results of that form to be entered into the gradebook by the core libraries
3) some way for an activity to request display of the grades (suitable for displaying within the activity, eg assignment view.php page).