AMQP input - more queue settings

[mgrzybek]

The Python implementation of carbon-relay uses random queue names to consume messages. This can be a problem when:

• you don't want to loose messages in case of relay's crash;
• you want to acknowledge the consuming process;
• you want to consume the message with a pool of relays.

Three parameters should be added to the [amqp] section of the configuration file: durable = true # default is false msg_ack = true # default is false queue_name = "carbon-relay" # default is empty

Any absent parameter could let the daemon use the classic python carbon-relay behavior.

[Dieterbe]

@mgrzybek would you be interested in contributing this? cc @jnjackins

[mgrzybek]

@Dieterbe I am not a golang devoloper but I can give it a try. These changes are minor.