Setup data/interface/domain apps

[ashiazed]

We want two django apps:
data - constants.py, models.py (where models are imported) and one model per file
interface (for the api)

We will also have a folder for the domain logic, it doesn't need to be a Django app.

[hyshka]

The frontend code is also a Django app, so we can change that up, too.

[ashiazed]

Yup, I'll move the frontend app into the interface folder after we merge #11