Fixes for Dataset Management

## Tasks
 - [x] Fix cascading delete
 - [x] Editing competition scoring program/etc doesn't seem to work?
 - [ ] On smaller viewport widths the buttons are too large and make each row take up 2 rows **Ignoring this for now, can't replicate in Chrome locally so putting off to finish other tasks**
 - If you unselect a dataset it doesn't warn you that you still need a dataset. I.E. edit competition, select new reference_data, save, edit competition again, unselect reference_data, save -> screwed up competition
    - [x] Check that reference_data and scoring_program are set, they have to be, fail form if not