All the dataz

Summary:
- Add more demo data and remove previous demo-data migrations
- Move existing data into the demo-data group

Refs T158

Test Plan:
- Run `minion migrations:run --up --group=demo-data` and watch your db fill with delicious dataz
- Run `minion migrations:run --down --group=demo-data` and get an empty site again

Reviewers: shadowhand

Reviewed By: shadowhand

Maniphest Tasks: T158

Differential Revision: https://phabricator.ushahidi.com/D44