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
Merge "Alter models and add migration"
Merge "Start server message changed"