Queue based Events

Thank you for this great module. We have been using it for a few different projects.

While there are Job Events, there are not Events currently for the Queue itself. It would be useful to know when the queue mechanism itself has finished, just like the UI based batch mechanism.

I started a patch that adds events to the start and end of the Queue process. It works well and if you would like to add to it more, please do.

Patch to follow in first comment.