Removed EntityTransaction until it has a real purpose. Added the affected entity to OptimisticLockException. Updated functional optimistic locking tests accordingly.

[2.0] completed implementation of lazy loading for Collections. Created debug helper class. Fixed default for orderBy clause to ASC

[2.0] Refined implementation and semantics of the merge and detach operations. General cleanups and API improvements. Added a testcase for detaching/serializing->unserializing->modifying->merging to demonstrate the transparent serialization.