DEV-9829. Added element versioning support in L2.

git-svn-id: http://svn.terracotta.org/svn/ehcache@7706 b9324663-ca0f-0410-8574-be9b3887307d
DEV-9829 (rev 7706, 28189, 23157 and 23155) merged from trunk.

git-svn-id: http://svn.terracotta.org/svn/ehcache@7707 b9324663-ca0f-0410-8574-be9b3887307d