[2.0] DDC-412 - Fixed YAML Driver not allowing multiple lifecycle callbacks per event. Backwards-incompatible change

[2.0] DDC-414 - Changed semantics of preUpdate Event to allow only changes to the entity changeset, not the internal state of the entity anymore.

[2.0] DDC-358 - Refactored UnitOfWork Event triggering capabilities -  Removed check for EntityManager instance. This is deep in the code and can hardly be get wrong.

[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] Merged PreInsertEventArgs/PreUpdateEventArgs => PreInsertUpdateEventArgs since they were identical.