[5.0] Improved session and authentication service.

I don't get your story.

@iRedds means add extra field to 'ci_sessions' table. By default 'ci_sessions' table has 4 fields: id, ip_address, timestamp, data.
For example laravel has 'user_id' field inside session table, which can be used to make feature like 'sign-outs all other devices except current one'.