Alter models and add migration

We must have correct models i.e. models that correspond
a database schema to use sqlalchemy features.
Update models.py and add migration script to correct
database schema and get rid of the difference between
schema and models.

Partial-Bug: #1365436
Change-Id: I9b4571906d39bcdb35048caa58d16ad5e888cce4
Start server message changed

The way that the user message was generated when it's launched a
server providing a configuration file was causing an error. This is
because the Message class doesn't support concatenation.

Change-Id: I05d475049f96057b06d3ae14ec33e0125b9c4dd5
Closes-Bug: #1369390
Remove reliance on import order of oslo.db mods

This change fixes a couple of import statements that rely on some import
order and a bit of magic to make the oslo.db.options module visible
under the oslo.db package without importing it explicitly.

The old version of the imports relies on Python's import machinery to
attach sub-modules to packages after import (see
http://paste.openstack.org/show/148711/). It is safer to explicitly
import the module we need, to ensure that we are not relying on
side-effects of importing other modules to configure global state for
the application.

Change-Id: Ia2772030915061ff373e7b7dc77f161146b56e59
Use testr directly from tox

Invoking testr directly lets us pass arguments to it through tox so we
can, for example, only run a subset of the tests.

Change-Id: I21351880db0848b860e7c61d4a8c711be2a49de0
Merge "Alter models and add migration"
Merge "Start server message changed"
Merge "Remove reliance on import order of oslo.db mods"
Merge "Use testr directly from tox"