fixing bug #3976
bug #4007 :  Now the expired sessions are well closed after a given time out as expected
fixing bug #3924
fixing bug #3553 by :
- fixing silverstatistics cron
- strengthening method which determine size of data directory
- throwing exception when a scheduled job fails
bug #4106 :  The lifecycle of the session management service is now managed by the IoC container (Spring). In order to remove any use of the service implementation (SessionManager), some additionals methods are defined in the session management interface. By letting the session management lifecycle done by the IoC container, we can then specify specific dependency on another IoC managed beans like the scheduler. As the SessionManager depends on SilverStatisticManager, SilverStatisticManager single instance is now also managed by the IoC container. Yet, as the session management service and the SilverStatisticManager lifecycles are managed by the IoC container, they can be correctly perform their shutdown process before the JEE containers run their own shutdown process (within which the JNDI service is stopped, service that is used to fetch notification topics).