Manage Course takes a long time to load

[20wildmanj]

Current behavior

Whenever 'Manage Course' is opened, if the course statistics are not calculated beforehand (i.e. not cached), the rendering gets held back by having to calculate assessment averages over the entire course. This means that it takes a long time to load the page, just to access settings.

Either we should asynchronously load the course statistics, or we should put it in a separate page.

Screenshots

Current Manage Course view. The averages are shown on the right-hand side.