Update process title when queues are paused

[PeterJCLaw]

If a queue is paused there isn't currently a way to see that from the outside. The process title ends up being "Waiting for items", which is a bit confusing if there are items in the queue (which there likely will be for a paused queue).

This isn't immediately trivial as the Backends handle the pausing and doesn't expose that to the Worker. One solution might be to have the worker more aware of pausing of queues.