Retain due dates when duplicating assignment

[birkyg]

When duplicating an assignment that has different due date/times for different sections, these due date/times should be retained in the duplicated assignment. Instead, they are lost, which partly defeats the purpose of duplicating assignments and is inconsistent with what happens if there's only one due date/time for all sections (in which case the due date/time is retained).

[ChristinaDrabik]

I agree. When we duplicate an assignment we want the duplicated assignment to have all student related information and submission related information preserved. Then we will edit the new duplicated container and add new assignment content and also edit the submission deadline dates.