sorry, tiny commits.
I've seen around the database task a few day.
I noticed this had some no good codes (consistency, global method ...and more).
I've tried to fix these problem before trying #5547, #6648 and some improvements.
Change an order of methods for readbility.
Change the behavior of db:test:clone task when schema_format is sql f…
Change the behavior of db:test:prepare task when schema_format is sql…
… for consistency.
Add a description about ENV["SCOPE"]
Remove session_table_name method because this is global and used only…
Move to db:structure namespace, because these methods are global.