[eclipselink-dev] Fix for bug 304251 checked in

[christopher delahunt <christopher.delahunt@xxxxxxxxxx>]

304251 - can not call EntityManager.merge on Entities with MapKeyColumn 
and ALCT
https://bugs.eclipse.org/bugs/show_bug.cgi?id=304251

First patch was checked into trunk and EclipseLink 2.0.2 on Friday.  
This latest check in is only into trunk.  It is a minor refactoring of 
ContainerPolicy's createChangeEvent to be abstract, and then 
implementing createChangeEvent within CursorPolicy to throw an 
operationNotSupported exception when called.  And also includes a change 
to DirectCollectionMapping missed in the original fix

Reviewed by Guy Pelletier