Add a way to navigate from a topic consumer/producer/queue to the owning handle/creator

[mutability]

Please add a way to get the consumer/producer creator that created a particular producer/consumer/queue

i.e. something like:

::kafka::kafka create kafka_master
kafka_master consumer_creator kafka_consumer_creator
kafka_consumer_creator new_topic kafka_consumer thetopicname
set handle [kafka_consumer info handle]
# now $handle == kafka_consumer_creator

This is useful because there are some things such as output_queue_length which belong at the handle level because they're shared at that level, but which are useful to use when you're dealing with the individual producer/consumer commands. Having to pass around both the creator command and the consumer command is awkward.