Implement and test Akka Actors for aggregate instance management

[iskandersierra]

• AggregateInstanceActor: executes the logic of an aggregate for a given aggregate instance
• AggregateInstanceSupervisor: supervise a collection of instances
• AggregateCommandRouterActor: picks the correct actor instance to send commands to
• AggregateEventsLoaderActor: Load events for an event store and sends them to the given instance
  • IEventStreamReader (Event Hub, Azure Table, SQL Table, ...)
• AggregateCommandFetcherActor: Picks commands from the command queue and route them to the corresponding actors
  • ICommandQueueReader (Azure Queue, Service Bus Queue, NServiceBus, SQL Table, ...)