Threadpool APIs and thread-related configuration service interfaces.

EventBusServiceInterface - Service representing an event bus. The service acts as message router between event producers and event consumers.
ScheduledThredPoolServiceInterface - An extension of the simple pool of threads able to schedule work to be executed at some point in time.
ThreadFactoryServiceInterface - Service representing a ThreadFactory instance. It is directly useful in Java world,
where various library pieces need to create threads and you may want to inject a customized thread implementation.
ThreadPoolServiceInterface - Representing a simple pool of threads able to execute work.

Change-Id: I4bb9c3fb118f317816ee24c7edaa292f8780ae32
Signed-off-by: Milos Fabian <milfabia@cisco.com>