"All [They've All] Got to Do" or Supplemental materials can be added, edited, and deleted

**Please do not merge this prior to #258 , as this is a branch off that**

Name says it all.

To get to these screens, start at `/admin` and follow the screens until Supplemental Materials is hit. Remember to clear your database first.

@andrewmaier Ready for review and/or styling love. Moving forward, I'll next work on People editing for Central Admins. I'll branch from here.