Allow setting publish and consume methods' options

[nfantone]

• Users may now configure additional options for channel#publish and channel#consume methods in the .client() and .listen() Seneca functions.

require('seneca')()
  .use('seneca-amqp-transport')
  .client({
    type: 'amqp',
    hostname: 'rabbitmq.host',
    publish: {
      persistent: true
    }
  });

• Replace some var usages -> const in unit test files..