Jack's Session class: Manage user access sessions stored in a database

This class can be used to manage user access session information storing and retrieving in from a SQL database.

It can start a new sessions creating the respective database records, if the session identified cookie does not exist or the session is expired.
The class can also terminate a session deleting its database records, set the session expiry time, verify set, get and delete session values, update changed sessions.

The class uses a separate database access class to remain database independent.