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

[2.0] DDC-321, DDC-323, DDC-324 - Implemented way to define UDFs from PHP in Sqlite Driver and registered to required default callbacks for SQRT and MOD, allowing functional tests for DQL MOD and SQRT to pass for all platforms.

[2.0] More general work on the SchemaManager and Platform classes. Making API more complete and adding sqlite and mysql test coverage.