Create an auditing event that allows the entire message stream to be consumed

[uglybugger]

We're going to need this for auditing, at least, but more likely we'll want it for an "Ops Dash" style feature before that.

I'm thinking just something along the lines of:

public class TheAuditors: IHandleMulticastEvent<AuditEvent>
{
    ...
}

where the AuditEvent looks something like this:

public class AuditEvent: IBusEvent
{
    public BrokeredMessage AuditedMessage { get; set; }
}

Thoughts?