* Enforce mandatory session verification only for new logins
- Creates `AppMigration` base interface as a way to isolate migration logic, app migrations must implement this interface.
- Creates `AppMigration01` with the existing logs removal migration and `AppMigration02` with the logic to allow existing sessions to skip verification.
- Add `DefaultSessionPreferencesStoreFactory.remove(sessionId)` to allow a ephemeral session store access to exist outside the `SessionScope` for this new migration.
* Fix tests
* Add more tests.
This also includes creating several abstractions.
* Review changes.
- Make `orderedMigrations` a class property, `migrations` just a constructor parameter to avoid incorrect usages.
- Create `lastMigration` property too, use it instead of `MIGRATION_VERSION`.
Benoit Marty