The BpmActivitiListener event listener is automatically added to the process when a model is created. BpmActivitiListener implements the ActivitiEventListener interface (see http://www.activiti.org/userguide/#eventDispatcher). The listener is responsible for creating and modifying BPM entities when some process events occur (e.g. a user task entering,
process cancelation, task completion, etc). This is the listener that creates ProcTasks objects and sets the endDate value for a ProcInstance.
