Initial draft code for swapping out rabbit

[dcramer]

• rq and psq support
• scheduler requires redis
• qa'd the rq adapter locally, but still need to test psq
• still need to implement k8s config for pubsub
• need to write tests for the various code paths

[dcramer]

@tonyo made solid progress to get rid of the rabbitmq spof - got it mostly stable locally. Could move around pieces of code yet, this was just a quick skeleton that I came up with. It mostly feels fine, though there's some weirdness around layout.