Adds DB support

- [x] Adds Sequel
- [x] Add data/models to the load path
- [x] Adds DB setting to .env
- [x] Adds migrations task(s)
- [x] Adds a console to test with

FYI - I haven't been adding docs up until now. This is the first merge that'll include enough to document. Let's just make another issue for adding docs, and keep them up to date from there.