Workflow Core 1.6.9

This release adds functionality to subscribe to workflow life cycle events (WorkflowStarted, WorkflowComplete, WorkflowError, WorkflowSuspended, WorkflowResumed, StepStarted, StepCompleted, etc...) This can be achieved by either grabbing the ILifeCycleEventHub implementation from the IoC container and subscribing to events there, or attach an event on the workflow host class IWorkflowHost.OnLifeCycleEvent. This implementation only publishes events to the local node... we will still need to implement a distributed version of the EventHub to solve the problem for multi-node clusters.