Meetings need to be editable by an instructor

[LoganDSPrice]

An instructor should be able to modify the start and end dates/times for any meeting.

Example: A meeting was automatically generated for Memorial Day. Class was not held on Memorial Day and was rescheduled to a couple days later.

We should also implement removing a meeting from a resource. This would also require updating (and retransmitting) submission scores.

[jelaniwoods]

Should an Instructor also be able to remove a Meeting? Say, a Meeting was generated for Memorial Day and Class will not be held that day and will not be rescheduled. Can an Instructor add/delete meetings after they're generated?