Allow leaders to set a later opening date for instructor/assistant sign up
Allow activity leaders to set a later opening date for instructor/assistant leader sign up for an activity. Right now, you can only set a registration date for participants. Instructor opening date is automatically open as soon as the activity is on the website. This allows instructors/assistant leaders to sign up for activities potentially before the leader is ready for sign ups -- for instance, while a course is in the unpublished status, or when an activity is a backup date that the leader might not want to fill until the originally scheduled date is canceled. It would be better in such circumstances if the leader could set a later date for instructor/assistant leader sign up.