Support nanomsg transport

[bitmage]

Problem: I don't want to setup/maintain a kafka cluster.

Solution: I'm writing in support for nanomsg in a fork:

https://github.com/bitmage/zdb

Still in the middle of writing the nanomsg implementation, but you can see how I've moved Kafka into it's own plugin under src/transport.

This is kind of a significant refactor, and I was just wondering what the level of desire would be to merge such changes back in? I'd be willing to work to make that happen, but if there's no desire to merge then I could simplify the design by removing layers of queueing/threading that are redundant with nanomsg.

Just want to feel out the current maintainers' thoughts on whether this transport abstraction would be of value to the project.

Thanks.

[bitmage]

Here's a diagram of the inheritance hierarchy for Connections.

https://docs.google.com/drawings/d/1C-b5hCN0SwKREtbx0xIN0c37EGWcm-dWSvj8mpudi_w/edit?usp=sharing