allow queue size to be configurable and use an array as local queue as t...

...he broker is single threaded

We were using a `Queue` in the Zmq broker, but the broker runs in it's own thread so access does not need to be synchronized when storing data for the local queue

Also elevated the backlog of the broker queue to be managed by an environment variable as we are seeing greater throughput with queue size being 25% of worker size which is also configurable via ENV variables

@localshred