Flask-session2

- Added support for `SESSION_COOKIE_SAMESITE`

- Changed `werkzeug.contrib.cache` to `cachelib`

- SqlAlchemySessionInterface is using VARCHAR(255) to store session id now
- SqlAlchemySessionInterface won't run `db.create_all` anymore

- SqlAlchemySessionInterface is using LargeBinary type to store data now
- Fixed MongoDBSessionInterface delete method not found
- Fixed TypeError when getting store_id using a signer

- Fixed signing failure in Python 3.x
- Fixed MongoDBSessionInterface failure in Python 3.x
- Fixed SqlAlchemySessionInterface failure in Python 3.x
- Fixed StrictRedis support

Added support for non-permanent session.