Allow to bind properties from property files from resources.

-- Fixed logback dependency
-- Strange existing cglib dependency moved to the root POM.

• Introduce @DB(transaction = REQUIRES_NEW) mode
• Introduce @DB.retries to automatically restart transactions after dead locks
• Introduce manual db-context handling using UnitOfWork.begin()/end()
• Rework multi-unit persistence concept, persistent-units now related to EntityManager, not the method annotation.