AMQP-162 Fix ExchangeParser for binding-arguments

JIRA: https://jira.springsource.org/browse/AMQP-162

AMQP-162: Addressing PR's comments

Improve `headers-exchange` parsing and `What's new` section

Polishing
AMQP-39 Add AmqpMessageBuilder

Fluent API for building messages.

Add equals() and toString() implementations for Message and MessageProperties.

JIRA: https://jira.springsource.org/browse/AMQP-39
AMQP-39 Polishing; PR Comments

Biggest change is to break out a separate MessagePropertiesBuilder.

However, the MessageBuilder uses one as a delegate so that the
fluent API can be used directly on the MessageBuilder without
having to build a separate MessageProperties first.