miniqueue

• Change abrupt client disconnect log level from error to warn

• Publish Docker image

• Add exponential backoff example
• Improve disconnect error handling

• Add dackCount to subscriber payload to enable exponential backoff.

• Add DACK command, can be used for delaying reprocessing of a message by a period of time.

Add negative acknowledgement support

This release adds two new commands for the client to send.

• NACK - Negatively acknowledge the message, returning it to the front of the queue.
• BACK - Negatively acknowledge the message, returning it to the back of the queue.

As well as minor fixes and improvements.

Stability improvements, concurrency bug fixes.

MVP supporting pub/sub with commands INIT, ACK and NACK as well as disconnect handling.