[michalovits]

• Adds AMQP Imposter, a configurable, model-driven AMQP 0-9-1 server to exercise client code against unusual interactions; amqp_imposter/README gives an overview of the "how" and "why"; amqp_imposter/model defines what the server can send or receive at a point in the interaction, as well as how to sample from this bag of sendable methods.
• Adds an rmqapitests suite, fuzz, that uses it in an initial batch of tests.