Database isn't documented very well

[aezarebski]

BLOCKED

Currently the database is not documented, which probably makes it much harder for people to use it downstream. Moreover, if we want to change things, it is harder to know what we need to make sure we preserve, i.e. what is relied upon in downstream usage.

In Issue #11 there is discussion of changing the schema slightly though so any documentation will need to wait until that has been resolved.