Allow to pass a script in config to do custom db migrations

The others ticket from the epic will allow us to prevent any data loss for the user when a migration is executed. The user will be able to rollback to the previous Drive version but the version will be fixed as the auto update will be deactivated.

the concerned users won't be able to update Drive anymore without removing the engine database and losing most of their datas.

 A possible fix would be to allow Drive to load a specific migration file throught the config. This file would be executed instead of the normal migrations and fix the database, allowing the user to re-enable Drive updates. 

The script could be:

• Python code that would be imported and used in Drive.
• A file containing SQL commands that would be executed on the Database.

A reflexion should be made about how to secure those file and prevent execution of malicious commands/code inside Drive.