Provide tools to migrate the config or the data between releases

We have been lazy in the past, by not provided tools to migrate from one version to the other, simply because they were milestones.

There are three things we need to migrate :

• configuration
• schemas
• data

for each of those data, we have to provide a tool that helps the migration from one version to the next one.

Ideally, this should be cumulative : ie, migrating from N to, say, N+3 should migrate those data from N to N+1, then N+1 to N+2 and finally N+2 to N+3