Add more challenge/status filters to activity when CHALLENGE_AUTOGRADE is selected.

[ZakGriffith]

A handy filter would be to have checkboxes for each challenge, and a dropdown for the status when CHALLENGE_AUTOGRADE is selected in the Activity component. Status either being accepted or rejected. So one could select a single challenge, or multiple challenges then filter it even further by selecting a status.

This would be beneficial for seeing a quick view of the quantity and status of the submissions for each challenge to help identify bottlenecks or issues.