#2669 Change Allura's amqp to zmq
Allura stores task info in mongo now, and only uses AMQP to notify taskd daemons that there are new tasks in mongo. Zmq is a better fit than AMQP, and also lets us fix the issue where the AMQP queue is growing and not being consumed properly.
Zmq should be optional (not a requirement), just like AMQP. README doc needs updated for this change too.
Zmq would require that web hosts be configured to know about the taskd hosts, or have our own broker.