Added AMQP adapter & updated Beanstalk adapter

I've created an adapter for AMQP and in doing so updated the way messages are handled allowing the return of a message object. Works similar to the way models return entities allowing you to confirm and requeue messages.

In doing this I've also updated the Beanstalk adapter to work in the same way and made everything use native Lithium classes/format.

Tests accompany both these adapters.