adding worker aggregate listeners (2)

retake on https://github.com/juriansluiman/SlmQueue/pull/76
Actually, I'd say that the base SlmQueue should not register any strategies but instead let each adapter specify the strategies. This way I could create a specific ProcessQueueStrategy for SQS that does a batchPop instead of the simple pop, and hence avoiding the complex process of unregistering strategies.

Having said that, what happen if one adapter would register a ProcessQueueStrategy and another one a ProcessBatchQueueStrategy? Will this enter in conflict with other strategies like MaxRunsStrategy?