[Course Pacing] exclude an activity from the course pace

Problem statement:

Some activities have roles that do not require a due date, but are tracked in the gradebook anyway. Currently course pacing requires those activities to be assigned a number of days to be allowed for completion, which requires a due date to be assigned.

Proposed solution:

Allow a duration of N/A to remove an activity from the course pace schedule, so that it doe not display any date at all.

User role(s):

instructor