Alter models and add migration

Update models.py and add migration script to get rid
of the differences between them.

Change-Id: I9b4571906d39bcdb35048caa58d16ad5e888cce4
Add ModelSMigrationSync classes

Add classes for testing correspondence between migration scripts
and metadata.

Change-Id: I0db68ea3557dd9d214ea50ff7c96de1a47a58d4b