core (memory/sqlite): changed history constraint /!\ Database schema change /!\ History was using a unique constraint on `profile_id, timestamp, source, dest, source_res, dest_res`, which can cause trouble because several messages send quickly by the same person can have a common timestamp (specially with delayed messages where precision is second), resulting in message loss. The new constraint use `profile_id, stanza_id, source, dest` where `stanza_id` is XEP-0359 stanza_id, so it's unique by definition, and no message should be lost anymore. Because sqlite doesn't support altering table with a constraint change, we have to create new tables and copy old data to new one, which can be pretty long. Sqlite update mechanism with "specifics" has been fixed when several updates are applied (e.g. moving from v5 to v7) and a specific is in the workflow.