UP-4143 EventSession purge fails to page, OutOfMemory can result

From ticket ...
As a uPortal adopter, I would like my portal to not run out of memory when it tries to purge a large number of EventSessions.  JpaEventSessionDao in purgeEventSessionsBefore() attempts to load all the matching sessions and then step through the list deleting them one by one, rather than loading them in smaller batches. This can result in an out of memory.

See uportal-dev@ thread re: http://thread.gmane.org/gmane.comp.java.jasig.uportal.devel/5743 .
I thought the the same thing too.  However, getting the delete of EventSessionImpl to cascade to the Many-To-Many relation (UP_EVENT_SESSION_GROUPS) was problematic.  I opted for this way.  This could be done better using scrollable results but that is a hiberate'ism. So, stuck with pagination approach and JPA.