Grade categories have a number of settings to "Aggregate only non-empty grades" and so on.

The problem is that some sites want settings always to be a certain way and would have to manually edit each category (could be thousands) to get what they want.

The solution is to add more options to a new grade category settings page to force certain settings: admin/settings.php?section=gradecategorysettings.

By default none of these are set. If they are set, then

 - those specific form controls on the category editing pages should be disabled,
 - any editing of that form should force those vales into the grade_category table (for completeness), and:
 - any code that depends on those values should check for and use the sitewide value instead of the actual value


Grade category settings -------------------------------------------------

Aggregation: [Menu of options here, including "Don't force" as default]
Aggregate only non-empty grades: [Force: On / Force: Off / Don't force]
Include outcomes in aggregation: [Force: On / Force: Off / Don't force]
Aggregate including subcategories: [Force: On / Force: Off / Don't force]
Keep the highest: [Menu of numbers, and Don't Force]
Drop the lowest: [Menu of numbers, and Don't Force]