Weighted Mean Extra Credit

We added extra credit to the Weighted mean of grades grade category aggregation method.

Before

Previously, Extra credit was not allowed on grade items within a Weighted mean of grades aggregation.

After

Now, Extra credit can be applied to items within a category whose aggregation is Weighted mean of grades.

![Weighted Mean Simple View After] (https://tigerbytes2.lsu.edu/users/pcali1/gradebook/after_gradebook.png)

Item selected to be aggregated as Extra credit will simply add their values to aggregated amount.

![Extra credit In action] (https://tigerbytes2.lsu.edu/users/pcali1/gradebook/in_action.png)