Generate sample data

Sample data should be created to enable client testing against use cases. A non-exhaustive list of examples:

- Add several messages from many geographic locations.
- Add message with varying combinations of Bluetooth IDs, Locations, some with and without the other.
- Create messages which go beyond the fourteen day limit to ensure clients don't receive them.

Feel free to get creative. We need _at least_ twenty entries, ideally at least 50.