1. Simplify the exposed api to reduce race conditions
which could occur if we allowed flow details, task
details and log books to be deleted at different
times; reduce this down to just being able to save and
delete from logbooks (and only save/update for flow
and task details to) to reduce the problem cases.
2. Introduce a alembic migration with a proper schema so that
the initial database can be created in the first place,
adjust its exposed fields and relations to be defined
by said schema.
3. Use oslo db models instead of our own.
Change-Id: I78bbedf87d506d3f39157198638937c933235b7b
dc56ff482a