Change database from sqlite to postgresql

[andrewsiah]

Might be more robust?? Not priority as of yet. Other things & features & debugging are more important if none of the features are dependent on PostgreSQL. As this requires learning docker, postgresql, and server (heroku) database interaction. Quite a significant leap without a lot of exact tutorials. Worth it, but frustrations ahead. Leap when ready.

Some tutorials:

1. A docker + postgresql guide
2. postgresql + django guide
3. django official doc on postgresql