Fill test database from models description

Now Heat models are the same as the tables state in DB after migrations,
so we can use metadata.create_all() to fill a test database.
This will speed-up test database creation and reduce a necessity in DB
migrations on SQLite

Change-Id: Ib7b6ab2591c01e91d7a55f3384dae505fe1485a7
Merge "Fill test database from models description"