A quick refactor - all users vs current user
Passing in null for the last paramter is rather pointless - especially because it turns out hashSync only takes 2 params
Hooked up user memory cache and logging in functionality.

SessionID should be unique now that i append an index to the front of it nowso we can use this for persistant cookies later too.

Lastly I prevented users from logging in when they are already logged in - it wouldn't help but it would create a new entry in the memory cache