POE component to manage queues and worker pools

 POE::Component::JobQueue manages a finite pool of worker sessions as they
 handle an arbitrarily large number of tasks. It often is used as a form of
 flow control, preventing a large group of tasks from exhausting some sort of
 resource.
 .
 This module implements two kinds of queue: active and passive. Both types of
 queues use a Worker coderef to spawn sessions that process jobs, but how they
 use the Worker differs between them.