89: Track session usage.
Was already tracking createdDate and lastModifiedDate.  Now tracks lastAccessDate, which accurately tracks the life of a session.
Added logic to SQLite schema handling that will rename the database file if the schema version changes, instead of deleting it.
That way, a migration can occur later so that the data is not lost.
See comments at end of class.spIrcSessionDAL_SQLite.php for migration SQL.