[2.0] More cleanups for recent lazy-loading implementation and minor object hydration improvements and cleanups. Collection refactoring part I for ticket #2352.

[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.

[2.0] Moved locking tests into Functional namespace. Fixed several missing flush() calls in some functional association tests. Reordered DELETE statements for ecommerce model tests in OrmFunctionalTestCase in order to maintain referential integrity. Fixed issue with bi-directional self-referencing one-one associations. Some other small improvements and cosmetics. Small hydration performance improvement through inlining method call in UnitOfWork::createEntity().

[2.0] Fixed issue with self-referential one-to-many associations not being persisted correctly when IDENTITY key generation was used. Included now passing OneToManySelfReferentialTest.