adds ability to delete multiple datasets

Resolves issue #624

## Functional Review

- Go to "My Datasets" page
- Select datasets to delete using the the checkbox on the right side of the table
- You can also shift select many datasets at once
- Press delete button, it should ask you to confirm
- After confirming page should refresh with datasets properly deleted

## Tasks
- [x] Shouldn't be able to delete other's datasets
- [x] Confirms before deleting
- [x] Shift select many
- [x] Test view
- [x] Test view permissions