EventHandler interface should shut down the event based plugins properly

Current Situation
the EventHandler interface will be used by the some plugins, e.g. the FactPlugin and the JobStreamsPlugin.

• the event processing will be started in a C++ thread and creates a separated Java thread per plugin
• the plugin stop (on JobScheduler shut down) will be started/executed in a C++ thread
  • This has the consequence that:
    • the EventHandler plugins are waiting for each other
      • e.g. when the event processing waiting for a event response from the JobScheduler
    • slow JobScheduler shutdown - the JobScheduler is waiting for plugins. For example if you operate the JobScheduler Windows service than terminating the service from the control panel can take 30 seconds and result in a warning of the service panel. This warning can be ignored.
    • when the plugins shutdown takes too long, the plugins execution will be aborted and will not close properly (e.g. the database connections not closed properly)

Desired Behavior

• the plugins shut down should not block the JobScheduler shut down
• all plugins should be closed properly on the JobScheduler shut down